One of my favorite math books ever is finally available in a semi reasonable way now! It's in that unfortunate limbo where it's protected by copyright, but it hasn't been printed since 1981 (by Dover! I love Dover.). It was always easy to buy a used copy, but I don't know how many copies ever even existed in the first place.
Anyway, now if you create an account with the open library, you can borrow the book to read in browser! It's not the best possible outcome, but it is at least alright.
As for the book itself, it's this wonderful little whirlwind tour from counting to the basics of calculus in less than 200 pages. It's really beautifully presented, and I can't recommend it enough if you're in need of such a book. I've really been afraid for the last seven years, since I discovered it, that it might suddenly be impossible to buy, and that no one would have made it available digitally in the meantime. It's such a good resource, and I'm so glad to be able to recommend it more widely now.