One thing I always find interesting with people getting into Warhammer 40k is when they get exposed to the real grim dark lore. They see the Imperiurm and it's problems and go that's a bit dark. Then they find out about the Corpse Starch, Haemonculi surgeries and Slaanesh in detail and go... oh.

I meanwhile had an idea that it was... way darker than it's been shown many times haha...