The Rachel Morgan books have held on pretty securely to their position as my favorite urban fantasy series for a while now.
The series is drawing to a close and the last few installments have moved towards the series endgame in such a satisfying way. Rachel has grown so much since the first book. She's wiser and tougher and more capable, but still recognizably the same person. Her personal growth, the battles she's fought, slowly revealed themselves to be pivotal to the future of the Hollows world. Her choices have become increasingly more important, the consequences more dire.
That being said, The Undead Pool is probably my least favorite of the recent books. In retrospect, I appreciate what it accomplished--the elves' religion had been a blank slate until this book, and Harrison finally fills in that gap. But I found the main plot confusing and hard to follow, which is a first for the Hollows series.
The developments on the romantic front made up for that--Rachel is ending up exactly where I want her, and I couldn't be happier.