I tried to read some of the earliest Warhammer novels and couldn't get into them for whatever reason. But today, I started looking at some of the Warhammer omnibus editions at the local bookstore, and many of them looked realllly interesting. I bought one... or two...

but really want to try some of the others as well.
So what are your recommendations, particular recommendations for omnibus editions? I've heard great things about Dan Abnett and Graham Mcneill, but of course, there are always some people who don't like them and recommend someone else instead.

Also, as Warhammer is a really complex setting, which books are best for people who are fairly unfamiliar with the setting?
I'm interested in Warhammer 40,000 because right now, I have a space opera/military fiction jones. But I'm also intrigued by some of the fantasy ones as well.
P.S. FWIW I did download the two free Warhammer ebooks from Black Library. Both were books from authors I had been interested in, so we'll see how I like them.