Finding Simon Petrikov

Marceline has only two goals to fulfill if it takes the rest of her immortal life: to find away to save her best friend in the whole world Simon Petrikov from loosing his memory completely and to hunt down and kill the vampire by the name of Marshal Lee that bit her and took everything away from her that she knew and love. But when she finally finds him and spares him, Marceline finds herself falling for the vampire on her quest to save Simon. Will she open up and finally learn to love again? Or will she shut him out? Read to find out. Sorry this is kind of a dumb summary, the story is much better. Also, this is an Adventure Time fanfic but you don't have to know what that is to like the book.