Stiefvater, Maggie. Sinner. Book 4 of the Wolves of Mercy Falls series. NY: Scholastic, c2014. 357 pages.
I was well into this book before I realized it was the 4th book in the series. I have not read the previous three. Although it might have made a little more sense to read them in order, I still was able to understand what was going on. I do think I would have connected to the characters a little better with prior knowledge.
The story is told in alternating chapters, either by Cole St. Clair, a passionate but damaged musician and Isabel, the girl he can't live without. Isabel is determined not to get too involved again, and doesn't trust Cole, but she is not happy with parts of her life either. It doesn't help that Cole is also a sometimes-wolf. Throw in a reality show where unscrupulous Baby North loves to manipulate and ruin the damaged stars in the show and you will see why Isabel and Cole find it so hard to succeed.
The first three books in this series are Shiver, Linger and Forever.
Recommended for 9th grade and above.