The Phantom Tollbooth - Juster Norton

For Milo, everything's a bore. When a tollbooth mysteriously appears in his room, he drives through only because he's got nothing better to do. But on the other side, things seem different. Milo visits the island of Conclusions (you get there by jumping), learns about time from a ticking watchdog named Tock, and even embarks on a quest to rescue Rhyme and Reason! Somewhere along the way, Milo realizes something astonishing. Life is far from dull. In fact, it's exciting beyond his wildest dreams...