The Jeeves books by P.G. Wodehouse (Anything that can go wrong probably will, and in the absolutely funniest of ways.)
The Menagerie series by Tui & Kari Sutherland (What if all the mythical creatures were real and you discovered that they live in a wildlife refuge in your town?)
The Arkadians by Lloyd Alexander (Adventure packed and filled with characters that are all just a little crazy.)
The 13 1/2 Lives of Captain Bluebear by Walter Moers (This book is so weird that it's kind of confusing.)
Notes from a Small Island by Bill Bryson (Pretty much any of Bryson's travelogues could fit in this category.)
Escape from Mr. Lemoncello's Library by Chris Grabenstein (Zaniness and books! It doesn't get any better than this.)