Why I'm Writing a Book on Cryptography (2020)
cryptologie.net
cryptologie.net
It seems designed for the kind of person who isn't comfortable using something until they understand how it works under-the-hood, but doesn't actually need to do any under-the-hood work.
It assumes very little knowledge, and is light on math. Sometimes it's a little TOO light on math, and it left me confused because I was trying to understand a primitive more rigorously than the book could support.