I wanted this book for two reasons--first, I read the Paulos' best selling book, Innumeracy, and second, I like both of the subjects.
Paulos begins with a brief chapter on definitions of humor by historical philosophers and writers. It's pretty interesting--what is it that makes something funny? His second chapter uses some mathematical and logical examples to help approximate what is going on in most examples of humor.
Paulos' main thesis seems to be that the most common example of humor deals with setting up the unexpected incongruity. One of his examples is great. A perverted old man leers at a young virgin girl and says, "What goes in dry and hard, yet comes out soft and wet?" The girl blushes. The old man replies, "Chewing gum." In this example, the joke implied axioms (answers to his question) which were quite different than his chewing gum answer. The greater this incongruity is, the better the punchline (which is why sexual connotations are often found funny).
Other chapters discuss variations on this theme, culminating in a theory of catastrophe involving dogs and the model for whether they will fight or run away when confronted. It's quite interesting.
I really enjoyed the book, and found it to be quite thought-provoking. Paulos does a great job of explaining many tough mathematical concepts, including Gödel's Theorem. I didn't fully understand Thom's Theorem at the end, but that's okay. One thing to be aware of is that the book is short and leaves you wanting more.
I think anybody interested in math will find this book entertaining, even if they're not particularly excited by humor. I do think interest in mathematics is requisite to enjoy this book, however.