The Space Marine Battles books. I've read Fall of Damnos and Battle of the Fang, and liked both a lot. Reading The Hunt for Voldorius now, and liking it so far.
Plenty of Space Marine omnibuses out there. I loved the Grey Knights. Souldrinkers is also good. Blood Angels is good, despite what many here will say. Heh. Not overly complicated, but the main character is the definition of courage, honor, and all that crap. Plus Mephiston shows up briefly. Those are all I've read of SM omnibuses so far.
Eisenhorn and Ravenor are Inquisitors. Their omnibuses are my favorite BL things so far. Not huge battles, but some powerful characters sometimes square off. Great intrigue. And those nasty Chaos guys have really interesting plans, devices, etc.