I'm on book 27 or 28 (of 50+):
Black Library - The Horus Heresy
There are multiple series other than The Horus Heresy. It is a massive universe, with hundreds of books. Sci-fi/war
Warhammer 40k universe. Henry Cavill is developing a 40k series for Netflix... looks promising (he is a huge fan, and supposedly has full creative license). If done right, it will be amazing.
As an example see: