For a more theoretically backed approach Dan Boneh's book ( https://toc.cryptobook.us/ ) is a very good resource.
A book I enjoyed a lot, that straddles the line between approachable and theoretical with a focus on implementation, is Serious Cryptography by Jean-Philippe Aumasson (one of the people behind blake2/3, amongst other things): https://nostarch.com/seriouscrypto
My understanding is that Cryptography Engineering and Practical Cryptography address this and focus on using crypto in the real world rather than mathematics and theory.
This is funny, because an old buddy of mine who did a brief stint at the NSA let slip that they almost never compromise the algorithm, it's virtually always the implementation where the weakness lies.
Always the easiest path, defeat the implementation.