Dreadful by Caitlin Rozakis

"It's bad enough waking up in a half-destroyed evil wizard's workshop with no eyebrows, no memories, and no idea how long you have before the Dread Lord Whomever shows up to murder you horribly and then turn your skull into a goblet or something. It's a lot worse when you realize that Dread Lord Whomever is--you. Gav isn't really sure how he ended up with a castle full of goblins, or why he has a princess locked in a cell. All he can do is play along with his own evil plan in hopes of getting his memories back before he gets himself killed. But as he realizes that nothing--from the incredibly tasteless cloak adorned with flames to the aforementioned princess--is quite what it seems, Gav must face up to all the things the Dread Lord Gavrax has done. And he'll have to answer the hardest question of all: who does he want to be?"--