First, kudos to Grafton for not making this an "is for" title. I'm sure it gave her publisher heart palpitations, but it is a perfect title. It might have little to do with the plot, but it's still perfect.
As usual, I found the novel meandering, but not haphazard. Grafton often has separate plotlines going, and she often pulls from other books to keep them spinning throughout her universe. What I ended up wondering is if this villain will be Kinsey's best, greatest solve, which is why Grafton is letting it roll out over several books. I don't agree that this is the darkest of Grafton's series - I can think of several others that have just as chilling or creepier endings. It's certainly true that this is the most ambivalent ending of them all.
Also, I have to wonder if Grafton is making some allusion to the usefulness of the Internet (which doesn't exist yet in the alphabet series) in how Milhone eventually learns crucial background about the villain. Or perhaps not. Perhaps she's simply touting the "old-boy" network.