Bloodsong - Melvin Burgess

Sigurd has a fabulous but frightening future predicted: even to start, he must leave everything he knows to go and fight a dragon, and from there descend into the Underworld. Sounds bad enough, but when you know that the dragon lives on a futuristic, industrially-ruined moonscape that was once Hampstead Heath, the scene is set for a staggeringly brutal fight on an epic scale. Unhappily for him, he meets the love of his life in the underworld, and Sigurd's efforts to rescue his lover will cause huge heartache and grief for both of them, and also for everyone who ever meets them.