The Phantom Tollboth, by Norton Juster, 1961

What's the point to anything a kid is taught at school? That's what Milo wants to know. To him, neither school nor pastimes have any rhyme or reason to them. But when a mysterious tollboth appears in his own bedroom, he drives off in his electric car to a land where idioms spring to life, where everything -- and nothing -- is literal, where allegory and admonition abound yet are never unwelcome. Delightfully written and illustrated, refreshing and funny and thought-provoking. Strongly recommended.