A 90s classic is the Warhammer 40k book series, “Eisenhorn” by Dan Abnett. The books in this series revolve around the inquisition agent known as Eisenhorn who hunts demons. The books take you on dark adventures across the vast human imperium from city worlds to ancient eldritch kingdoms on the far fringes of the universe.  

Throughout the books Eisenhorn goes to extreme lengths to hunt down demons that lurk in night. In the process, he must make hard choices and sacrifice a lot to keep humanity safe. The books can be very dark. They feel very much like film noir in space, and they remind me of certain authors writing styles, like HP Lovecraft. It feels like a very grim, dark version of mass effect at times, too. The universe is portrayed in a very detailed manner. It feels like it is almost real with its depth and horror. The franchise, on the other hand, is the polar opposite of “Star Trek,” with a human empire that partakes in witchcraft and nukes entire races out of existence. 

“Eisenhorn” creates a very lively, vast, bleak, futuristic universe. The books are part of the much larger Warhammer IP by The Black Library. The books can dive into very mature sexual themes and certain occult moments, so I would not recommend it to kids. However, nothing in Warhammers 40k book series is safe for kids. Check it out and be wary of heresy.