Rose of the Prophet

A little-known and underrated fantasy trilogy by Margaret Weis and Tracey Hickman, Rose of the Prophet manages to transcend its genre and create a beautiful and believable world/cosmology, memorable and lovable characters, and an entertaining and quite moving story--all while conforming to the rules and structure of your standard Dungeons & Dragons-style role playing game. Really--has to be read to be believed.

Most of the action takes place within the cities and deserts of an Arabian Nights-esque land in a multi-faceted world of magic and adventure. There is crisis among the One-And-Twenty Gods and their attendant Immortals; two Gods have diminished into non-existence, the gods all blame each other, and one God fears the conflict will soon spread to the human realm as jihad, holy war.

The Wandering God Akhran tries to unite two feuding tribes of his desert nomads against the threat, by commanding the marriage of Princess Zohra, of the shepherding Hrana tribe, to Prince Khardan, Caliph of the horse-herding Akar...but seeing as Chaos and Impatience are two of Akhran's attributes (and his people are faithful followers indeed), it doesn't go as well as Akhran might have wished.

Akhran convinces Promenthas (a God of a medieval-Europe style land across the ocean) to ally with him, and they arrange for the young wizard Mathew (lone survivor of a slain ambassadorial party) to wind up among the feuding nomads. Khardan, Zohra and Mathew, along with their tribes' djinn and a guardian angel, must somehow prevent a massive army from conquering the mortal world, a vastly overpowered efreet from banishing all other Immortals, and one god from eliminating all the others--and shattering the cosmic balance forever.

The three books are:

Volume 1: The Will of the Wanderer
Volume 2: The Paladin of the Night
Volume 3: The Prophet of Akhran

Tropes used in Rose of the Prophet include:

Actual Pacifist: Mathew considers all life sacred. When he's forced to kill Meryem to save Khardan's life he suffers a minor BSOD but that's nothing compared to his shock when an out-of-control spell accidentally kills thousands!

Auda: There is no war in your land? The magi do not fight?
Mathew: I do not fight!

Affably Evil: Auda Ibn-Jad.
Asexuality: Mathew can feel love for both men and women, but never experiences sexual desire for any of them. This is something the people of Akhran find difficult to understand.
Attractive Bent Gender: Mathew is mistaken for an extremely beautiful woman.
Arabian Nights Days: The setting, mostly. When it's not wandering entirely off the planet or into time-travelling dream cities.
Arbitrary Skepticism: A lot of characters drift close to this sometimes, most egregiously Mathew, who despite being a sorcerer doesn't believe in the existence of djinn- and even after he accepts their existence (having been witness to their powers multiple times) still doubts the existence of angels, who are part of his own religion! (Oddly, even though he doubts the existence of angels, he's fully prepared to believe in the existence of devils, although admittedly he had just summoned one at the time.)
Being Tortured Makes You Evil: "The Rebirth", the procedure the Paladins of the Night use to replenish their depleted ranks; captured Worthy Opponents are tortured by the Lifemaster until they are utterly broken and pray to Zhakrin to accept their loyalty in exchange for release from their torment. Khardan thwarts this due to the similarity in the sounds of "Zhakrin" and "Akhran".

Auda: Naked, covered with blood, we are born into this world...

Belligerent Sexual Tension: Zohra and Khardan. The highlight of their wedding night is Zohra stabbing Khardan. And it doesn't improve by much.
Blondes Are Evil: Meryem.
Blood Brothers: One of the traditions of the Paladins of Zhakrin. Catalus was the brother of Auda, obligating Auda to fulfill the death curse Catalus placed on Feisal. Auda taking Khardan as his new brother is the defining point in their relationship for the rest of the series.
Butt Monkey: Usti, the comically overweight, much-abused djinn assigned to Zohra by Fedj (who actually does so as an act of revenge against Usti for some unspecified slight).
Cain and Abel: Sort of. Khardan and Achmed eventually end up on opposite sides of the conflict when Achmed becomes Qannadi's adopted son and most loyal general, but neither is considered the "bad" one.
Chess with Death: Pukah challenges Death to a bet- if he can survive one day in Serinda, the city she rules where all the imprisoned Immortals die and are resurrected every day, she must free them all. He wins, thanks to Asrial.
Chekhov's Gun: Other that more powerful magic (such as that which allows the holder of their mortal dwelling place to command a djinn) Cold Iron is the only thing than can restrain an immortal. Like Kaug.
Cold Iron: The main weakness of all Immortals- it can't hurt them, but it can bind them and render them powerless. A common threat used against the djinn is being locked in an iron box and put somewhere nasty where they'll never be found. Pukah defeats Kaug by tricking him into entering an entire mountain made of the stuff.
Deal with the Devil: Mathew deals with an Imp of Astafas in The Paladin of the Night and nearly loses his soul before he finally rejects it.
- Asrial makes a deal with Death to betray Pukah in exchange for letting her go free to protect Mathew in his darkest hour. Or at least it seems like she does- although she delivers Pukah's protective amulet to Death, instead of leaving she takes Pukah's place and sacrifices herself to let him win his bet with Death.
Deliberate Values Dissonance: Prevalent throughout the story. Mathew is shocked and bewildered by the brutal and simplistic worldview of the people of Akhran, who have little regard for the sanctity of life, even though they are generally good honourable people.
Does Not Like Men: Zohra holds all men in contempt, although she gets along well with Mathew and eventually warms up to Khardan.
Dungeons & Dragons: The cosmology is based on a twenty-sided die, with references to D&D character alignments.
Even Evil Has Loved Ones: The Paladins of Zhakrin are about as evil as they come, but they set a GREAT store by loyalty, family and brotherhood.
Exact Words: Fedj convinces Zohra to stick out her marriage to Khardan by pointing out that while it is Akhran's will that they remain married until the Rose of the Prophet blooms, he did not specify that the marriage had to be consummated.
Expy: While a lot of the setting has similarities to real world cultures and religions, Promenthas is in almost all respect the New Testament Judeo-Christian God, complete with a hierarchy of angels and tenets of love, peace and universal brotherhood.
- Additionally, while he's only a single god in a pantheon rather than the almighty power above all, he's notable for being one of the few gods whose followers don't even believe in the existence of other gods apart from Astafas, Promenthas' evil opposite and Sularin's version of Satan (other gods' followers at least acknowledge the existence of the pantheon, even if they only worship their own god) making the Promenthan religion fundamentally monotheistic.
Female Angel, Male Demon: The only named angel of Promenthas is Asrial, although she does mention male angels (and a few nameless ones are seen in Serinda; the only example of one of her evil counterparts we see (an Imp of Astafas) is male.
Femme Fatale: Meryem.
Fish Out of Water: Mathew.
The Fundamentalist: Many of the characters in the series are driven by their beliefs to some extent or another, but Feisal the Imam of Quar is utterly devoted, body and soul, to his god.
God Is Flawed: Pretty much all of them are to some extent, some more than others. For example Akhran, despite being a noble and honourable warrior god, couldn't organise his followers into an egg-and-spoon race (unsurprising considering he's the god of Faith, Impatience and Chaos).
Gods Need Prayer Badly: One facet of the conflict.
- Actually the main cause of the conflict- Quar wants all the Prayer for himself.
The Grim Reaper: Death in the series takes the form of a classically beautiful woman with 2 empty voids where her eyes should be.
Green-Eyed Monster: Zohra hates Meryem from the moment Khardan brings her back to camp with the intent of adding her to his harem even before Meryem tries to murder her and she and Mathew realise Meryem is a spy for the Amir.
Grey and Grey Morality: Despite gods and their followers in the world of Sularin being openly labelled as good, evil and neutral, almost nothing is as simple as it seems. Khardan notes Zhakrin's Paladins of the Night initially seem to be cruel and heartless monsters, but are caring and loyal to each other; Auda Ibn-Jad is unquestionably an almost immeasurably evil man but risks his life to protect Khardan when they become Blood Brothers, even though Khardan tricked him and eventually sacrifices his life to avenge his earlier brother Catalus. Most notably, the final conflict isn't between the forces of good and evil, but the forces of chaotic neutral (Akhran) and lawful neutral (Quar).
Guardian Angel: Every follower of Promenthas has one and they are the lowest tier of the angelic hierarchy. Asrial is Matthew's. Apparently a demon of Astafas is legally obligated to warn you if they are not present before you make any deal with them regarding your soul or its ownership.
Guile Hero: Pukah, although he has a tendency to stuff up hilariously.. Also Matthew to an extent; while a powerful sorcerer in his own land, he's bereft of most of the tools he needs to work his magic for the majority of the story and has to survive on his wits.
Honor Before Reason: Khardan shifts around this trope a bit, ranging from simple Pride Before Reason to a steadfast Faith Before Reason.
I Love You Because I Can't Control You: This is what keeps drawing Khardan back to Zohra despite everything she does that antagonises him- with every woman in his tribe willing to throw themselves at his feet, Zohra is the one woman who never gives him a inch. The story even mentions as such when Khardan refuses to take another wife after marrying her, noting that Zohra makes other women seem boring by comparison.

There were times, however, when he admitted to himself that the eyes of the sparrow were dull and lackluster after one as looked into the fiery black eyes of the hawk.

I Owe You My Life: Mathew decides after Khardan saves his life that even if his life isn't worth living for himself, he'll live to pledge it to Khardan's.
It Is Pronounced "Tro-PAY": At once point when Mathew snaps in his frustration at how much he misses his home he goes off at Zohra for constantly pronouncing his name "Mat-hew". While attempting to calm and console him she tries pronouncing it "Matchew", which touches him and when he calms down he apologizes to her.

Mathew: I'm sorry. And Zohra, you have been speaking my name... just fine.
Zohra: Of course. I knew I was saying it right, Mat-hew. It was you who were not hearing it right.

Jerkass: Meelusk the fisherman, a miserable, shrivelled, selfish old bastard who is described as being so low that even the followers of Benario the Thief God spit on him in contempt.
Jerk with a Heart of Gold: Although much of it can be attributed to her being the Tsundere Rebellious Tomboy Princess of a harsh people in a harsh land who grew up without her mother's guidance to boot, Zohra really can be unnecessarily nasty sometimes. She does truly love her people though, even if she holds most of them in contempt (to be fair, she holds almost EVERYONE in contempt).
- Likewise, Khardan is honourable, noble and honest, but he's also capable of being a real ass sometimes. His cluelessness about Zohra's feelings gets him into NO end of trouble when he brings Meryem back to camp for the first time (he thought she'd be PLEASED that he wanted to take another wife, assuming that he'd "tamed" her as a result of their last Ship Tease moment).
- Between the two of them they take Belligerent Sexual Tension to the level of actually wanting to see the other die in pain and disgrace! It's little short of a miracle that they finally admit their love for each other once and for all.
Last Words: "Many fine sons..."
Love At First Sight: Pukah towards Asrial.
Magic Music: Asrial has the ability to sing a beautiful song that puts those who hear it to sleep. Whether any other Immortals share this ability is unknown as the only time it is used in the series is when Asrial puts Pukah to sleep so she can take his form and die in his place, allowing Pukah to win his bet with Death.
The Mole: Meryem.
No Guy Wants an Amazon: The reason Zohra remained unmarried for 22 years before her enforced union with Khardan was that as soon as her father announced her eligibility for marriage all the single young men of the tribe either hastily married or headed for the hills and didn't come back until she'd publically sworn that no man would have her. Khardan eventually comes to see that Amazons have their good points. (Auda also finds her incredibly attractive.)
Obfuscating Insanity: Khardan decides that the only way to spare Mathew's life (the people of Akhran consider him an abomination for dressing in women's clothing) is that he is insane (they believe insane people saw the face of Akhran just before they were born and are blessed by the god). Mathew goes along with it to save his life and ultimately finds a way to use it to his advantage.
Our Ghouls Are Creepier: Classic Arabian ghuls, man-eating shapeshifters who man the ship leading to the island fortress of Zhakrin's paladins and take their payment in human flesh, although clearly distinct from djinn.
Pre-Mortem One-Liner: Auda gets a good one.

Feisal: Give me a knife...
Auda: Here, my lord.

Proud Warrior Race Guy: This is more or less the hat of the people of Akhran- the horse-riding Akar are the most warlike, but even the sheep herding Hrana have their pride and will fight at the drop of a hat and the camel-riding Aran are pretty much the same.
Runaway Bride: Zohra tries to flee her marriage to Khardan (after failing to disembowel him at the altar) but is coerced into sticking it out by Fedj.
Save Your Deity: At the climax of Prophet of Akhran, Khardan decides that even if he dies and his people are exterminated, he can save Akhran by reaffirming his faith in him when tempted by Feisal.
Scary Black Man: Raja, Sheykh Zeid's gigantic ebony-skinned djinn.
She Cleans Up Nicely: Zohra usually doesn't make any effort with her appearance, considering her femininity more of a curse than a blessing. But the story notes that when she does go to the effort she's stunningly beautiful and she knows how to use it.
Small Name, Big Ego: Pukah is convinced he's the cleverest and most handsome of all immortals... and causes no end of trouble as a result. He's not entirely without talent, being cunning, quick-thinking and daring, but his abilties don't even come close to his overinflated opinion of himself.
- He eventually realises how badly he fell into this trope, how much trouble he caused and how even his successes were largely due to others and redeems himself with a truly brilliant Thanatos Gambit Heroic Sacrifice that defeats Kaug the Efreet and single-handedly turns the war in the heavens against Quar.
Threat Backfire: Khardan walks right into this one when, during a fight between his people and Zohra's, he calls off one of his men attacking her to take her himself:

Khardan: Death will not rob me of my chance to see you humbled, wife!
Zohra: Oh, won't he? (slashes his leg with her dagger)

Tomboy Princess: Zohra; her character introduction notes that her father indulged her and let her run wild in his grief over her mother's death and by the time he tried to reign her in it was far too late. (The one time he threatened to beat her she snatched the stick from his hand and threatened to beat him instead!)
Tsundere: Zohra, like you would not BELIEVE.
Two Lines, No Waiting: There are at least three plots that intertwine, affect each other, and sometimes reflect each other.
Unresolved Sexual Tension: Good grief do Zohra and Khardan keep it up for along time -- the entire trilogy, only being brought together by Mathew on the very last page of the third book.
The Vamp: Meryem.
Wedding Day: The biggest fiasco this side of the Ranma1/2 finale, with both parties constantly insulting each other, the bride having to be dragged to the altar bound and gagged, the groom made to attend literally falling down drunk, the bride attempting to gut the groom as soon as the knot is tied before fleeing and the entire affair breaking out into a bloody brawl until Sond brings the tent down on everyone to prevent casualties.
Wham! Line: At the end of the first book when the man in the white palanquin catches up with Mathew again.

Auda: In the name of Zhakrin, God of Darkness and All That Is Evil, I command you all- sleep...."

Wicked Cultured: Auda again.