Going to just pin this here so as to collect the links in one handy thread and also so I don't have to go searching for old threads at some point in the potential future.
The Fighting Fantasy Series (Popular gamebook series from the 80s)
The Gamebook Adventure Series (A digital gamebook series, duh)
Grimdark Graphic Novels (Various graphic novels for edgelords)
The Worldwar Series (Regular scifi novel series)