Synopsis: George Beard and Harold Hutchins, the co-stars of Dav Pilkey's Captain Underpants series, are back with their second graphic novel, the sensational saga of two silly caveboys named Ook and Gluk. Life is pretty sweet in Ook and Gluk's hometown of Caveland, Ohio, in 50,001 BC-even though they're always getting in trouble with their leader, Big Chief Goppernopper. But things take a turn for th terrible when an evil corporation from the future…