An eye opener for me professionally was when I accidentally read Katz and Lindell's
Introduction to Modern Cryptography and a rigorous text on the reverse engineering of the Enigma at the same time. I don't remember the title/author of the latter, but I remember I was reading it for pleasure, and I was also digging for something in the former for work. Some googling for you turned up a nice expository Master's Thesis
https://core.ac.uk/download/pdf/144149789.pdf
I've always been a romantic when it comes to math, and by then I had tired of the usual high-level spy drama. I wanted to know the science of how it works. Any thorough academic text on cryptography will quickly show you that our ideas today aren't as new and exciting as we think. For example, all of the mathematics for the most popular public key algorithms had all been laid down by Gauss and Euler long before Diffie and Hellman, or those RSA guys wrote down their algorithms. The only part missing was the modern computational need to drive the application.
And poor old G.H. Hardy thought he wasted his life with "silly" math only good for solving puzzles in the back pages of whatever magazine he was reading.
https://www.math.ualberta.ca/mss/mis...%20Apology.pdf
The essay above really illustrates the backwards nature of the cryptography story...oh I won't ruin it for you. I would recommend starting with this essay, then the masters' thesis, then...at least that would be my "wax on...wax off" baby step approach for any student who inquired.