I very much enjoyed The Rook when it came out a couple of years ago (and I wouldn't have read it but for Viccie). I ordered it on my tablet and waited to read it until I was on vacation, which was very disciplined of me and highly inconsistent with my personality.
In this book, Myfanwy Thomas is brokering a deal to merge two covert supernatural organizations: her own Checquy and its more-or-less equivalent from the continent, the Grafters. But someone doesn't want it to happen and begins staging significant attacks on the organization. Predictably, the two long-term enemies begin blaming each other and contemplating not going forward with the merger. Myfanwy enlists two young women--one from each organization--to help her stop the carnage and complete the merger.
One great thing about this book is that there are 3 central female characters who are all well-written, have different personalities, and have believable interactions that are unconnected to a man. So it REALLY passes the Bechdel Test. Usually applied to movies (which almost always fail it--books are better), a form of entertainment only passes the Bechdel Test if there are 2 named female characters who talk to each other about something other than a man. it's shocking how few movies pass.
But that's a different issue. Back to the book. Another great thing is that it's not all incredibly serious. There are some laugh-out-loud lines and many strong chuckles in the book.
And finally, the history between the two parties makes it clear that the mutual suspicion and hatred were appropriate and the plot rumbles along nicely and convincingly (once you accept the supernatural element, of course).
If you are interested in this type of story, I would highly recommend it. But if you haven't read The Rook, do so first.