Is that book really that old already?

I love Christopher Moore. If you read all his book chronologically, there are elements that carry through into other books, as well as recurring characters. And if you don't read them that way, you aren't missing all that much and still get excited when you see an old friend pop up in a new book. (The only book I can think of that doesn't have recurring characters is Fool, because it's a King Lear parody.)

The vampire trilogy I enjoyed mostly for the extra characters: the Emperor (who shows up in many books), Chet the enormous cat (my mum has a cat very much like him and I want to get him a red sweater!), the Animals, and especially Abby Normal.

In fact, it's often because the secondary and tertiary characters are very engaging that I enjoy the stories so much.

One of the very best of CM's book is A Dirty Job.