I enjoyed this very much while I was reading it, despite a slight disappointment because initially I was shipping Olivia and Phaedra. ;-) It's a smoothly written novella, and can probably stand alone if you haven't read the rest of the series. A nice quick read if you enjoy besotted paranormal heroes. (The heroine is human, but also a witch, so has some powers of her own.)
After reading it though, I felt here was a build-up that went unrealized. The title comes from Sebastian thinking he's one of The Wicked and thus unworthy of Olivia. That never made much sense to begin with and doesn't go anywhere.
Also, if you're sensitive about disability themes, this might bug the hell out of you.