Our Infinite Fates - Laura Steven

They've loved each other in every lifetime. They've killed each other in every one.

Evelyn can remember all her past lives. She can also remember that in every single one, she's been murdered before her eighteenth birthday.

The problem is that she's quite fond of the one she's in now, and more importantly, her sister needs her for bone marrow transplants to stay alive. So now she has to-

1. find the centuries-old enemy who hunts her through each life and destroy them forever
2. figure out exactly why she's being hunted in the first place,
3. try quite hard not to fall in love with them

...again.