Door of Stone: Book One of the Juniper Holt Series

Juniper Holt is eighteen years old.
She has very little to worry about - getting good grades, overdue fines at the library, and avoiding her annoying neighbor, Brad. But when a quick trip to the library on a blustery winter day turns into a car accident and an abduction, everything changes.
Now Juniper has to worry about getting home. She's been taken to another realm, where she encounters a group of four people who call themselves Halvfødt - or half-born - and speak of things like gods and magick. These people say they're from her past, a past she can't remember, and she wouldn't believe them, if it weren't for Axel.
Axel, who had apparently been her childhood best friend. Juniper only has glimpses of him in her memory, young and care-free, but it's enough to convince her that she really did know him, once. Enough for her to follow him through a hellish realm and confront the twelve years of her life that she can't remember.