You got it wrong, Djvu. Ryan was Vicepresident for just a few hours, not for a complete book.
Complete series of Jack Ryan, named in cronologic order. I own all of them and have read'em quite some times.
1-Without remorse (precuel)
2-Patriot Games (Ryan vs Irish terrorists)
3-The hunt of the Red October (Best Clancy novel ever-period)
4-The cardinal of the Kremlin (theme: Star Wars)
5-Clear and Present danger (Drug Wars)
6-Sum of All fears (A-bomb in denver)
7-Debt of honor (War vs Japan)
8-Executive Orders I and II (Ryan as President)
9-The Bear and the Dragon I and II) (last Ryan books so far
in Clear and Present Danger, Ryan gets to be interim Subdirector of the CIA (Intelligence) in substitution of the ill and then dead Admiral Greer.
In Sum of All Fears, Ryan is Subdirector of the CIA, leaves the job at the end of the story.
in Debt of Honor, Ryan returns to the government as National Security Advisor (thanks sikboy:)) As a reward for his good job, President Durling rewards him with the Vicepresidency -vacant because kealty's sex scandal-.
During the ceremony of Ryan's nomination as vicepresident, the 747 crashes into the Capitol killing almost all the government, except for the non-present members of the congress, Alan Trent, and Jack Ryan, who was in an annex building and who immediately steps up as new President.
IMHO, there is not much more to write about Ryan. The Bear and the Dragon was quite nice but the end comes too...suddenly. Kinda reminds me "Red Storm Rising", Clancy's 2nd best book ever (IMHO), wich came to a very very sudden and drastic end...it left me with the impression that he didn't know how to end the story and had to "cut it down" by any mean possible.
Anyway in the "Ryan's universe" there is not much more to be told or done

. Quite sad because I like Clancy's novels about Jack Ryan -even when I find them too much idealistic and american-centered for my "foreign" taste

-, and the other series (Op-Center) is utter BS.