R is for Richochet (by Sue Grafton)
There was a time when I'd go back and re-read the series periodically. But I don't think I've re-read any of them since K is for Killer. I can always go back and do that if I am in the mood for more Kinsey Millhone.
(Did you know that Sue Grafton always gives characters in the book the same initials as the book title? This book centers around a girl named Reba, for example. But she always throws in some totally irritating non-names. Reba's father is named Nord Lafferty, of all things. Nord.)
I feel like this one is better than the last few (not that I remember the last few all that well). I remember liking all the ones up to K, and liking M, and being vaguely disapointed by the rest. But it's basically a book for fans of the series. If you want to know which one I'd suggest as the best, it's G is for Gumshoe. That one is my favorite.
On a side note, I like reading the bad reviews of books on Amazon, and I noticed that there's invariably a bunch of people who complain that the book contains gratuitous sex. This is pretty much applicable to any book with sex in it.