He was mailing it in, the last 5 or so Jack Ryan books were also co-written, which probably means he sketched the plot out a bit and handed it off to whoever was ghostwriting. I think I stopped at the Bear and the Dragon, which I think was pretty mediocre too. I can quite clearly remember the plots and details of all of the books up to and including Rainbox Six despite not having read any of them in 10+ years, but I have barely any recollection of the Bear and the Dragon. Come to think of it, I don't really remember much about Executive Orders either. Debt of Honor was the last really good one IMO.