But more importantly, the novels were consistent with each other. The books all had a timeline in the back, and I made an effort to keep the "Marvel novelverse" coherent and consistent. So, for example, Dr. Octopus's appearance in the "Doom's Day" trilogy picked up on his previous appearance in Diane Duane's The Octopus Agenda.
That timeline wasn't in all the novels. The books I have have the timeline in the books starting around the 1997 printings. But it was from that timeline that I found "Mutant Empire" occurred before "The Venom Factor".