One of my favorite mathy kids' books is back in print. In The Cat in Numberland we visit Hotel Infinity, with its infinite rooms, all full and yet they always seem to be able to make room for new guests.
Good for ages 5 to
adult. (It's $19.95 plus over $9 shipping. I think they should charge less for this slim volume, but this
book is so wonderful, it's worth it.)