Ask HN: Older textbooks/papers you consider classics still worth studying today?

When I was an undergrad (enrolled in 2011) I decided to screw my professors book recommendations and lookup what the internet seemed to think was the best book in each subject and read that instead. Most of them were fairly old. Some examples that I remember off the top of my head:

Intro to CS: SICP (1979)

Algorithms/data structures: CLRS (1989)

Theory of computation: Sipser (1996)

Compilers: Dragon book (1986)

Calculus: Spivak (1967)

Linear Algebra: Dover's by Shilov (1971)

The given year is for the first publication, some of them are still being updated and I probably read a newer edition.

PAIP - Norvig 1992. It appears to be available online https://github.com/norvig/paip-lisp

Claude Shannon's original 1948 paper "A Mathematical Theory of Communication" launched the entire field of information theory. It's 50 pages, highly readable, and pedagogical. The source of its magic is that Shannon introduces and concretely grounds an essentially new ontological concept of vast applicability. And it has 100,000 citations.

http://math.harvard.edu/~ctm/home/text/others/shannon/entrop...

"Mathematics Useful for Understanding Plato", 100AD, by Theon of Smyrna. Amazing.

Not sure you’re looking for philosophy, but I keep a translation of the Tao Te Ching nearby at all times. It’s helped me stay centered and humble.

Just to go meta: whatever book you learned something from originally/in college you should keep. It might not always be the best, but keeping the context of your original understanding can really help and speed up recollection when needed. (This probably applies most to textbooks used for whole classes as opposed to minor topic references.)