tomswift2002: You've got the timeline all wrong. Let me explain.....
Okay, so the Marvel novels, of which The Gathering of the Sinister Six was but one of many, was co-published by Berkley Books and Byron Preiss Multimedia Company. BPMC was formed in 1992 to produce CD-ROMs of various kinds, right when that format was taking off. BPMC also developed Virtual Comics, about ten years before web comics would be a thing. While Byron had a privately owned book packaging business (called Byron Preiss Visual Publications), BPMC was a publicly held company with stockholders and such, and so it was BPMC -- which had investment capital -- that got the license from Marvel to do novels and anthologies, which debuted in 1994. (BPVP couldn't afford what Marvel wanted for that license.)
By 1999, the CD-ROM bubble had completely burst, plus the world (and the technology) wasn't quite ready for web comics yet, so both Virtual Comics and the CD-ROM business imploded. The Marvel novels were the only thing keeping the company afloat. Then Marvel cancelled the contract due to non-payment of royalites (because all the money being generated by the books was going to paying the electric bill and people's salaries, as literally nothing else was bringing in money at this point).
BPMC fell into the swamp, and Byron formed iBooks as a new book venture, entering a co-publishing deal with Simon & Schuster similar to the deal BPMC had with Berkley. He was able to renegotiate with Marvel -- blaming the stockholders and such -- and renew the license. It was under this imprint that the Sinister Six trilogy was finished, and they also did several X-Men books -- Michael Jan Friedman's Shadows of the Past, Steven A. Roman's Chaos Engine trilogy, Steve Lyons's The Legacy Quest trilogy, Karen Haber's Science of the X-Men, and the anthology Five Decades of the X-Men.
Adam's trilogy and Mike's novel were both commissioned by me for the Berkley/BPMC line, but were cut off by the cancellation. (I had commissioned several other books that never did see the light of day, including a Captain America/Wolverine team-up novel by Jason Henderson, a Daredevil novel by Warren Ellis, a sequel to Venom's Wrath by myself and Jose R. Nieto, a Spider-Man/Silver Surfer team-up by Steven A. Roman & Ken Grobe, and possibly one or two others that I don't recall 20 years later.) By 1999, I had left the company in disgust, as in addition to not paying royalties to Marvel, BPMC wasn't paying freelancers, either, and I got tired of screwing people I worked with and respected in order to service my employers, whom I worked with and totally didn't respect. For that reason, and others, the Sinister Six trilogy are the only ones that can be considered in continuity with the Berkley/BPMC books.
The last novel in Byron's new license was the last book in the Chaos Engine trilogy, which was published in 2003. Byron died in 2005, so his death had no bearing on those books at all.