This one is for anyone who understands basic math, I’d say usually around age of 8 and up. It’s fun to read for adults too. It explains rather “why” than “how” in a short and simple way: https://www.amazon.es/-/pt/Bitcoin-Money-Tale-Bitville-Discovering/dp/0578490676

More technical one for adults explaining the “how”, I’d recommend this one: https://www.amazon.es/-/pt/Mastering-Bitcoin-2e-Andreas-Antonopoulos/dp/1491954388

Even for non coders, it explains the “how” nicely and you can always skip what gets to technical.