Not quite as good as the two before it. The characters weren't as strong, and the one-liners were altogether a bit less frequent.
The entire thing felt as if it were exposition for books to come; retconning some stuff from the first two books to prepare for another book in the future. No idea if I'm right or not, but that's how it felt to me.
Not that it was a bad book; it wasn't. But I felt it was weaker than the first two, the characters were less developed and there was less comedy overall (other than a few sex jokes, which felt a little like cop-outs).