What can you say about Laurell K Hamilton that hasn't already been said? Yes, "A Stroke of Midnight" is full of graphic, gratuitous sex and yes, the plot crawls along to a rather unsatisfying climax (no pun intended) but in my opinion, the Merry Gentry novels are better than the recent Anita Blake efforts.
For one thing, there is a definite story arc here, whereas the last two of three Anita books have just gone through the motions, shoving a little plot where it'll fit around all the turgid bedroom scenes. Merry is still trying to get pregnant and her twisted cousin Cel is nearing the end of his imprisonment. Plot threads that began in earlier books are continued and expanded, and Hamilton has created a delicious world of faery magic and politics that will obviously continue to develop into the next book.
Secondly, the sex actually serves a purpose in the Merry Gentry novels. Whilst Anita becomes more of a Mary Sue/author surrogate with every man she beds, Merry must get pregnant to keep her life and save the lives of those she loves. Every time Merry does the nasty with another impossibly beautiful fey man, old magic is restored to the men and the sithen. Having said that, the sex scenes are far too long and a lot of the time they seem like filler rather than plot advancement.
Thirdly, Merry is a far more sympathetic character than Anita. She gets ahead by caring, first and foremost, and she wins more and more fey to her side in this book by being compassionate and willing to take risks for her people.
If you've read the first three books in this series, this one if worth picking up. I don't recommend it as a starting point for newcomers to either Merry or Hamilton; there's far too much you already need to know to understand the complex storylines. Overall, it's trashy fun and fills a few hours, which is really all I expect from this series.