The Phantom Tollbooth

Milo is bored by literally everything, including his own toys, until a tollbooth shows up in his room with no explanation. He drives his toy car through it anyway and ends up in the Kingdom of Wisdom, with a map of a place called the Lands Beyond he didn't ask for.

The kingdom runs on a joke that keeps paying off: everything is literal. Milo gets stuck in the Doldrums, where nothing happens, until Tock — a dog with a clock built into his side — explains that thinking is the only way out. In Dictionopolis, words are hawked off market stalls like produce, in a market run by King Azaz; in Digitopolis, the Mathemagician's people dig numbers out of a mine like gems. The two kings once had a working kingdom until they exiled their sisters, the princesses Rhyme and Reason, over an argument about whether words or numbers matter more, and Milo, Tock, and a blustering bug called the Humbug set out through the Mountains of Ignorance, past demons like the Terrible Trivium, to bring them back.

It's for kids who like puns enough to sit through a lot of them, and for anyone who wants a book that keeps arguing for paying attention, sometimes as a joke and sometimes flat out — Milo comes home having been gone for weeks by his own experience and about an hour by the clock, and the last thing he says is that there is too much to do right where he is, which is a softer landing than the rest of the book's cleverness really needs.