It is a must for anyone serious about UNIX programming.

Additionally one should get the TCP/IP and UNIX streams books from the same collection.

Is the Unix streams book “Unix Systems V network programming”?

That one is also relevant, yeah.

Although, I did a mistake, I was thinking about all Richard Stevens books for networking, that go beyond plain TCP, UDP, IP.

https://en.wikipedia.org/wiki/W._Richard_Stevens

Unfortunelly given their CS focus, they are kind of on the expensive side, I read most of them via libraries, or eventually getting my own copies.

It's been the standard reference for decades for a reason. I learned from it, too. There's really nothing else quite like it available.

It might mean the Baader–Meinhof effect.

It's well written and full of practical advice and fun to read.