[xashor]

Instead of the gawk manual, I recommend the OpenBSD manpage: https://man.openbsd.org/awk.1 It's concise and well written (as most OpenBSD manpages), so you can learn AWK even in less than 2 hours. Of course it handles only AWK, not the gawk extensions.

[nmz]

mawk also has a nice and short manual. since GNU decided to make its money selling books, their manuals are usually huge and that's by design.