Slave to Sensation by Nalini Singh

Slave to Sensation by Nalini Singh
Psy-changelings #1
334 pages

In a world that denies emotions, where the ruling Psy punish any sign of desire, Sascha Duncan must conceal the feelings that brand her as flawed. To reveal them would be to sentence herself to the horror of “rehabilitation”— the complete psychic erasure of everything she ever was….

Both human and animal, Lucas Hunter is a Changeling hungry for the very sensations the Psy disdain. After centuries of uneasy co-existence, these two races are now on the verge of war over the brutal murders of several Changeling women. Lucas is determined to find the Psy killer who butchered his packmate, and Sascha is his ticket into their closely guarded society. But he soon discovers that this ice-cold Psy is very capable of passion—and that the animal in him is fascinated by her. Caught between their conflicting worlds, Lucas and Sascha must remain bound to their identities—or sacrifice everything for a taste of darkest temptation.

This has very good world building.  It is definitely a new kind of character for a paranormal book.  I have not read anything like the Phy characters before.