I’ve seen a bit of it around but know nothing about it. I do love large world building with extensive story lines (I really enjoyed the entire Dune series, even the prequels his son wrote). So if I wanted to start reading WH books, where should I start?
Eisenhorn novels and Cain novels are good starts. I haven’t read gaunts ghosts but I hear they are cool as well.
The other thing I’d recommend is hopping in any 40K Wiki and clicking around until you find something that interests you then find a novel based on them. As long as you aren’t jumping into the middle of a multi book series you should be fine.