Don Quixote, USA by Richard Powell.
This isn't SF, Fantasy or classic but it's definitely clean and funny if you don't mind tongue in cheek stereotypes. Check the reviews on Amazon.
https://www.amazon.com/Don-Quixote-U.../dp/B008MZZ3FM
Maybe it is a classic. It's old enough since I first read it as a Readers Digest Condensed book probably sometime around 1964.