I didn't care for this. Witches (females - it's not clear to me if there can be male witches (warlocks?)) can apparently be forced to bond with demons. And demons appear to be any "Other" that is not a witch. So, the hero is a troll, which is apparently a low level demon. The heroine is a witch. The hero sees the heroine and immediately recognizes her as a witch and decides he wants to bind her to further his powers. The witch sees the hero and has no idea he's Other. She thinks he's human and she wants him. So, they have sex, she finds out what he is and they're bonded. That's pretty much it - no big deal for her. Next thing you know, they're in "love".
I didn't care for the "bonding witches against their will in order to steal their power" idea at all. I didn't care for the instant love. And I felt like I didn't know what the hell was going on with the "Other" world. There really isn't much world-building.