@joyce there's a stealth category of Supposed Kids' Books That You Should Absolutely Read As An Adult and that's my number two all time book on that list, the first being The Thirteen Clocks by Thurber - I know @neilhimself is a fan as well - an absolutely masterful book on every level. Everyone should get to know the Golux and the Todal. Anyone who loves The Last Unicorn is likely to love this book too
@KShortill@joyce I would certainly list the younger-audience works by @neilhimself to start with. He writes with respect for the minds of younger people, which is the key quality of a work like this. Calvin & Hobbes is a canonical text of this type, as are the first few Earthsea books by LeGuin. The Princess Bride novel is not, which surprises many who see the movie first. I've never written out an actual list so I'll have to think about it to recover a few more examples.