Its actually got a lot of really interesting ideas in it. The last two novels (there are four) essentially jump into completely unrelated to the game territory, but the characters you've been following are so good and the ideas so crazy it works.

As for the Mormons, they aren't treated as heroes, just that their survival prep and accumulated arms make them able to hold out. Corporal Taggart (doomguy) is a lapsed catholic (when he prays he in incapable of coming up with an image of god and ends up visualising the faces of the horrible abusive nuns from his catholic school) and Arlene Sanders had a brother who went Mormon and became a sexist jerk, so they are both pretty wary. The one Mormon who ends up coming with them is a good guy but also is having crisis of faith. The Mormons are pretty mad about Arlene being a combat soldier who is a woman too. They don't stay very long because they have to go kill more aliens of course.

Resisting the urge to nerd out on the cosmology established in the third and forth book lmao