William's Picks
Harry Potty and the Deathly Boring by Steffan Petrucha and Rick Parker
For those who liked Harry Potter:  funnier and with lots of  toilet talk.  A great parody.
The Adventures of Ook and Gluk by George Beard and Harold Hutchins
In my opinion this book is funnier than Captain Underpants. Lots of caveman talk.
The Adventures of Captain Underpants by Dav Pilkey
The original. Still the best in my opinion.
The Dodgeball Chronicles by Frank Cammuso
Funny book about Arty and his life in school. There are more in the series.