Yeah, that's what really drew me into the 40K universe, ironically. I loved sitting and reading the stories of Marine-vs-Marine and Titan-vs-Titan. There was a piece of artwork, I think it was a two-page spread, that had Marines fighting each other around some buildings, with Titans stalking the streets, and one of the columns on a building had a bunch of Marines strapped to it. Sadly, I can't seem to find that image online, and I'm not sure I have the book(s) still (salvaged what I could post-fire, but a lot of the books were in a location that wasn't safe). One more thing to look for whenever I manage to make it over to the used book warehouse across town.
Ah, back when Titans were such badasses, like this: