If I had to describe this book in a word, I'd call it a romp. It's fun, it's funny, it's a fast-paced adventure. And it's very clever. Too clever, in fact; one gets the impression that the author is very impressed with himself, and cracks himself up with how witty and clever he can be. 
 Somewhere on GoodReads, I saw a description of a book (don't recall which one) as "it's like a friend's little brother--he's really funny and entertaining for a little while, and then you want him to go away." That's an excellent synopsis of this book.