
I’m new to the books myself, but the general consensus I’ve seen online is to read about the factions you’d like. That’s why I picked Orks :) I got through a few chapters of Eisenhorn and it’s, so far, not quite as action packed as the Ork books I’ve finished but IMO has much better world and character building.
NSFW warning: https://youtu.be/giya5hahGec