Adrian Appel 
Riftbound [EPUB ebook] 

My Name is Lydia Park. Orphan. Juvenile Delingquent. Special Forces Soldier. Murderer. And, last but not least, something called a phasewalker. Connected with and able to travel through universes parallel to our own but invisible to the average human, I have abilities that the average person can only dream about. It»s made me of interest to many people, most of which wanted to use my powers to further their own means. Good thing I»m not someone to be pushed around — mess with me at your own peril. My Name is Park, Lydia Park, and this is my story.