I could read a good DOOM novel or three, sure. The "one" I did read was...er...disappointing?
Anyway, my thoughts: Don't "explain" the demonic hierarchy...hint at it maybe, but that's about it. The way I've always seen the DOOM demonic pecking order is one of "how many souls have you sent to hell and how painful did you do it"? Basically, a demon gains 'prestige' via how often and how spectacularly painful it kills. At a certain 'soul/pain' quota it gets a new body (re: "tougher" demon). Humans would be vastly preferred, counting as 'bonus points', but other demons count too (hence, in-fighting). No demon really "orders others" around based on some social hierarchy...the demons that can kill you in one or two hits call the shots because if you don't do what they want...er...they kill you in one or two hits. Pretty good incentive, especially if when a demon is killed it has to start as a weaker one and 'work its way up' the meat-suit line (former commando, sergeant, chaingunner, pinky, imp, etc....).
I'd like to see something that focuses initially on gung-ho "kill'em all" attitude...which then goes horribly wrong...leading to a "WTF am I going to do?!?" moment...leading to a..."I gotta get AWAY!"...persisting until the futility of it all sets in and we move into the final..."I'm as good as dead, but I'll be damned if I ain't gonna take as many of those demonic sons-o'bitches down with me!". End, roll credits. That's how I first 'saw' DOOM. I was a marine, ready to kick ass...and I did for the first few levels of imps, demons, sergeants and commandos. Then I got paranoid about every little shadow, as I saw my ever dwindling resources dip lower and lower...just getting to the next 'level' was the goal. Then once I realized there's pretty much no help and no turning back, a determined resignation to just blast the shit outta anything that moved in hopes of getting to the 'end'. A DOOM novel should reflect that character journey.
If you want more sci-fi over DOOM-Carnage, then I'd get into the behind the scenes guys; from the chairman of the UAC board, to the head engineer of defensive equipment, to the doctors, down to the receptionist. This would take a LOT more work to make it interesting, but I always wondered about other bases, ships, towns/cities, etc. I'm sure there are TONS of stories about these guys that could be every bit as interesting as reading about some marine with a god-complex rampaging throughout two dimensions.
PS: Definitely leave out anything about demons being "bio-engineered" or other DNA crap like that; demons are demons from hell and they want to chew your face off and feast on your soul. Deal with it.
Paul L. Ming, a.k.a., The_Hierarch on some other boards.