This has bugged me every time I've seen it. What do you think the deal was with Mel Gibson's character always needing to pick up a copy of "Catcher in the Rye" everytime he saw one???
In the movie it is one of the things that the government programed into him... if you'll recall they track him by the purchase of "Catcher in the Rye" at one point during the movie. I believe they got this idea from either Hinkley (shot Reagan) or Oswald (shot Kennedy), I think it was one of those two, or both, who had a bunch of copies of Catcher in their appartment.
I think it was also meant to imply that other assassins may have been created by the shadow group in the past, but Jerry is at a state before he was used to kill someone.