I haven't read all of the other books in this series, and I was initially worried that I would be lost - but that wasn't the case at all. I could tell that some of the characters were clearly from previous books, but this still worked fine for me as a standalone.
I'm pretty picky in my PNR reading because I don't like doormat and/or TSTL heroines and heros who behave like jerks and order the heroine around. This book avoided those cliches. I liked Lore and Idess very much. Lore - a half-breeed demon - is the ultimate bad-boy (an assassin), but still redeemable, and Idess - an angel - is a heroine that it is easy to root for. The conflict driving them apart was very real; Lore wants to save his sister and Idess wants to be reunited with her brother. They initially fight their feelings for one another, but in the end, they have the courage to take a chance on love. I could say good things about the world-building, the plot, etc, but really, the love story is the crux of the book and what I enjoyed so much about it.