Runemarks

Five hundred years after the end of the world, and goblins had been at the cellar again...

Maddy Smith has always been an outsider. Born with a rusty-coloured rune on her hand - what the villagers call a ruinmark - she is scarred by this symbol of the old gods, a sign of magic.

And everyone knows that magic is dangerous. Except for Maddy, who actually thinks it's rather fun. Until now. For suddenly her friend One-Eye, a rascally Outlander, wants her to open Red Horse Hill and descend into World Below - a world filled with goblins and far worse - to retrieve a relic of the old gods...

A novel by Joanne Harris, Runemarks is the story of Maddy Smith, a fourteen year old girl who is sent on a quest to retrieve an artifact of the old gods called the Whisperer.

Tropes used in Runemarks include:

And Man Grew Proud: With bonus Norse gods.
Embarrassing Nickname: Jormungand seems a little irritated when Loki calls him "Jorgi" for short.
Exact Words: How Loki got out of having his head cut offf when he offered it in a bet with the dwarfs and lost. He claimed that he had never mentioned his neck in the bet and, since they couldn't get his head without harming is neck, he kept his head on the technicality. However, he got his lips sewn together for his trouble.
Fantasy Kitchen Sink: Much like Norse mythology itself, with numerous mythologies referenced and indicated to be coexisting.
Fate Worse Than Death: The MO of imprisonment in Netherworld, complete with a gaoler appointed from the prisoner's worst fears.
Fiery Redhead: Thor. Played with for Loki who, although having a Wildfire aspect and the fire rune Kaen on his arm, keeps his temper almost completely in check.
God Was My Co-Pilot: Many times. A large number of people, including Maddy, turn out to be fallen North gods.
He Who Must Not Be Named: The Nameless.
Norse Mythology
Omnicidal Maniac: The Whisperer seeks to start the End of Everything so that it can create a new world where it is in supreme control of everything, a desire stemming from being used as, essentially, a Magic 8-Ball by the Norse gods.
Pals with Jesus- Maddy encounter, and in some cases befriends the entire Norse pantheon. And she's trained in magic by Odin One-Eye himself.
Primal Fear: The coin of the realm in Netherworld.
Scars Are Forever: Both Odin and Tyr suffer under this, inkeeping with the Norse myths. Loki's scarred lips also seem to be this.
The World Tree: Yggdrasil.
The Chosen One: Maddy turns out to be Modi, the one destined to rebuild Asgard.
Trickster Archetype: Loki, obviously.
Why Did It Have to Be Snakes?: Loki's biggest fear is snakes; rather ironic considering that the World Serpent is his son.