Hold onto your pants for this awesome adventure from the author of the million-selling Captain Underpants! Harold and George are back - presenting the sensational saga of two crazy kung-fu caveboys raising hell in 500,001 BC! Ook and Gluk have a pretty great life growing up together in Caveland, Ohio, even though they're always getting into trouble with their short-tempered tribal leader, Big Chief Goppernopper. But the boys' idyllic life takes a turn for the terrible when an evil corporation from the future invades their quiet town... With action, laughs, comic strips and flip-o-rama fun in every chapter, here's excitement aplenty to blow your pants off!

This ebook edition includes bonus material about the making of the books, sketches by Dav Pilkey, deleted scenes and more! George Beard and Harold Hutchins present the sensational saga of two silly caveboys named Ook and Gluk. Ook and Gluk have a pretty awesome life growing up together in Caveland, Ohio, in 500,001 BC - even though they're always getting in trouble with their nasty leader, Big Chief Goppernopper. But Ook and Gluk's idyllic life takes a turn for the terrible when an evil corporation from the future invades their quiet town.