Jack Ryan is an agent with the CIA.
At least he is at the beginning of the series. There are a few series where the main character enjoys promotion. Stephen Coonts' Jake Grafton rises from Lieutenant to Admiral. John LeCarre's George Smiley moves from a junior agent to the head of the agency. None, however, has such an advance as Jack Ryan.
From an analyst at the CIA to Deputy Director of Intelligence. On then to National Security Advisor, Vice-President, and finally President.
It is one helluva journey, told by a master.
Ryan was born and raised in Baltimore. He earned a degree from Boston College, attending NROTC at the time to earn a commission. As a marine, Jack Ryan served his country and earned credit under the G.I. Bill to return to college. Having graduated from college with a doctorate in History, Jack Ryan spent time as a stock broker, betting his own money on 'high-risk issues and scoring big'. Leaving this profession due mostly to boredom, he turned to writing and his big love, history. He taught for a time at the Naval Acadmy and it was there that he really became noticed and was finally approached by the Agency. At the beginning of the series, Ryan had worked for three years, on his own time, on a biography of Admiral Halsey.
Ryan's involvement with the CIA came as a result of his knighthood. While as a tourist in London, he 'unknowingly prevented the assassination of two very prominent figures' by terrorists. This earned him an honorary title and brought him in touch with many important people who would be valuable later in his life.
Having made these contacts and earning a reputation as an excellent researcher, Ryan is approached by the CIA where he quickly comes under the tutelage of Admiral Greer, who found in Ryan an excellent analytical mind. Ryan quickly moved up in the ranks until, at the start of the series, he is Greer's chief analyst.
Ryan is married to a highly successful surgeon named Caroline but called Cathy. They have four children. Since the series covers such a wide period of time, the children grow up and go out on their own. His son, Jack jr., eventually takes a job much like his father.
The majority of the activity in the series is before Ryan's days as President. Once he takes office, his actions are obviously quite a bit different than before but cloak and dagger features prominently nevertheless.