My 18-year-old brother really enjoys solving Rubik's cubes and other 3D puzzles, and enjoys math and physics at school. I'd like to get him a book on the math of the Rubik's cube, but one that makes no assumptions of experience with group theory or proofs. I reviewed Singmaster's notes on the subject, but they appeared too technical. I also found a few other promising books, but I couldn't download any samples to see if they would work.
What books provide the balance I'm looking for?
My go-to book for Rubik's Cube group theory is Adventures in Group Theory by David Joyner, altho it might be a little tough for someone new to the subject. To be honest a more friendly resource might be some websites I've seen:
https://ruwix.com/the-rubiks-cube/mathematics-of-the-rubiks-cube-permutation-group/
https://ruwix.com/the-rubiks-cube/gods-number/
https://en.wikipedia.org/wiki/Optimal_solutions_for_Rubik%27s_Cube