[Ransom]

That is, in fact, what worries me. Having not read the book myself, could you explain how, if they do, they differ from glorified space zombies? This is an honest question -- the Flood in the game seemed to me to be a silly plot device inserted after the developers couldn't think of a way to make the Covenant interesting antagonists, but I'd like to be proved wrong.

[Deepblue]

The flood were created by the forerunner as a weapon, but ended up destroying them. /hypothesis

It actually seems similar to the relationship between the ancients/shivans.

Oh, and I find the covenant far more interesting than the flood.

[aldo_14]

That is, in fact, what worries me. Having not read the book myself, could you explain how, if they do, they differ from glorified space zombies? This is an honest question -- the Flood in the game seemed to me to be a silly plot device inserted after the developers couldn't think of a way to make the Covenant interesting antagonists, but I'd like to be proved wrong.

Facehugger-created zombies, I thought.  Which would make them like HLs' headcrab zombies, but using guns....

I think they were interesting as a large swarm of enemies, engulfing by mass rather than individual power, but pretty crap when they became old fashioned zombies.  The problem with these sorts of open-ended questions (like the Shivans) of what the Flood are, is that usually your imagination makes the actual truth an anti-climax.