[devy]

> It’s really short on the crypto and offers no insight into why TLS behaves the way it does. ... It’s a lot of “using openssl s_client”-type of discussion;

That is literally how the author explained in his book's Amazon Kindle version's free preview[1]. The author specifically said he is not a brilliant mathematician so he's not going into the details of explaining the math but rather explain the how-to from a practitioner's standpoint. Obviously, you don't need to be a brilliant mathematician in order to under the math behind public-key cryptography but for many engineers, I agree with the author that I care more of about how to configure it and make it work securely rather than the reason behind the scene. The author also claimed that he would recommend some further readings if you would like to dig into it more.

[1]: https://www.amazon.com/gp/product/B091TBX4WH