The Dresden Files/Summer Knight

Book #4 in The Dresden Files.

In the wake of a personal tragedy and having pissed off every vampire around, Harry neglects everything in the hopes of finding a cure for the love of his life. However, he is pulled out of his blue funk by Queen Mab, who wants him to find who murdered the Summer Knight. Like with most anything involving the Sidhe, things get complicated very quickly as Harry rushes to foil a supernatural plot that could destroy the world.

Tropes associated with Summer Knight:
""Damned correspondence course.""
 * Anti-Magic: The Unraveling, which can undo any enchantment,.
 * Battle Cry: Two memorable ones.
 * Harry Dresden: I DON'T BELIEVE IN FAIRIES!
 * In the name of the Pizza Lord! Charge!
 * Beard of Sorrow: Harry starts the book on the tail end of a Heroic BSOD due to losing Susan in the previous book, during which he neglected his business and grooming.
 * Busman's Holiday: Billy invites Harry to his house to play some Arcanos with the Alphas. Harry grumbles that it sounds too much like his day job.
 * Big Good:
 * Call Back: Harry insists he really had nothing to do with the broken elevator in his office. It certainly wasn't because of a magical scorpion trying to kill him.
 * Chekhov MIA: Elaine.
 * Chekhov's Gun: Toot-toot and fairies similar to his status love pizza.
 * Convenient Decoy Cat: When Morgan showed up at Harry's apartment after arrived,  hid in Harry's bedroom. During Morgan and Harry's conversation, a noise comes from the room, prompting Morgan to investigate. He opens the door, and Mister zooms out, startling Morgan, much to Harry's amusement (and relief).
 * Death of a Thousand Cuts:
 * Disappeared Dad: Maeve the Winter Lady offers to give Harry what he wants in exchange for "his first born child". As in, she wants him to.
 * Einstein Hair: No one in particular, but the Trope Namer is refereed to by this hair by the Queen Mothers.
 * The End of the World As We Know It: What would have happened if Harry hadn't gotten involved..
 * Face Palm: Harry has a particularly memorable one here.
 * Fate Worse Than Death: Happens to the Winter Knight after the events this book. This has been different from most fates worse than death in that we have received updates on him more than once and, yes, he is still being tortured. The books take place in real time, very roughly speaking, with about a year between publication of each and a Time Skip of about a year or so between most books. Four books after what happens to the Winter Knight, Harry sees him, still imprisoned. Even Fix, who hates the guy is disgusted by how much he's suffering.
 * Food and Animal Attraction: When Harry meets Injun Joe for the first time, his pet raccoon goes immediately for the half of a chocolate bar in Harry's pocket.
 * Guardian Entity: The Queen Mothers' home was protected by an 18 hand unicorn.
 * The Hecate Sisters: The Summer and Winter Queens are each divided into three distinct and separate Fairies: Queen Mother (The Queen Who Was), Queen (The Queen Who Is), and Lady (The Queen Who Is To Come).
 * Heroic Sacrifice:
 * It Is Beyond Saving: Unfortunately, that would probably have doomed the whole world.
 * Leave Your Quest Test: After completing the task he's given at the start of the book, shows up and asks Harry whether he'll act on the newly uncovered knowledge that, or go home, knowing his job is done. After Harry chooses the former,  says that if he had answered otherwise, he'd have killed him right then and there.
 * Meaningful Name: Ms. Sommerset, aka, Queen Mab. "Sommer" equates to "Summer", thus making the name "Summer set." Not only a reference to coming after Winter but
 * Mother Nature, Father Science: All the Queens of Faerie are women. The Queen Mothers speak highly of Albert Einstein, referring to him as a sage.
 * My Hovercraft Is Full of Eels: Harry's attempts at speaking Latin do not go well.


 * Noodle Incident: Queen Mab knowing
 * Not a Game
 * Punny Name: A very subtle one. Dresden is being guided by a fairy so small, she only appears as a small bright red light that can blink on and off. Her name is Elidee (LED).
 * Rape As Backstory: One of the changelings is the end result of when a male troll raped a female mortal. Maeve also taunts Lily when they meet up in Proven Guilty, saying that she used to "dance" for Winter with Lloyd Slate at gatherings. There is a reason those changelings sought shelter with Summer...
 * Revenge By Proxy
 * Secret Test of Character: Many throughout the series, but a notable one was used here.
 * Also, the Summer and Winter Mothers give him one..
 * Take a Third Option: At the beginning, when all levels of Fae are choosing Summer or Winter's side, Toot-toot and his allies have not.
 * Wise Beyond Their Years: From the view points of the Queen Mothers of Summer and Winter who have been around for millions of years, they see Albert Einstein as this, calling him a Sage for his insight that energy can neither be created nor destroyed.
 * Yank the Dog's Chain: Harry briefly hoped