I started recommending the books just because they're free but realized pretty much all are at least okay or good, there don't seem to be many bad ones among the freebies. Maybe because writing a book and making it public takes deliberate and considerable effort, so only motivated authors do it.

Out of curiosity, how many of the free books have you used? Would you recommend any one over the others?

Some of the books I used are "Code with Repl.it", "Tpython 101", "Boxes", "Clean Architectures in Python", and "The Hitchhiker’s Guide to Python".

I highly recommend "Boxes: Your Second Python Book" because it's unlike any other book I've seen. It focuses on text layout algorithms and builds an increasingly advanced exmaple through successive iterations.

To be fair, similar applies to paid-for books. I can name two Python books that were pretty bad, yet seemed to be popular.