I first got interested in Repairman Jack after reading an excerpt from Cold City on the website criminal element.com.
At the time I knew nothing of F. Paul Wilson. But Cold City appealed to me because it took place in NYC of the 1990s. Since I am originally from NYC, I enjoy books that take place there and Cold City definitely had the sense of place that I have come to appreciate.
I mentioned to a friend that I was reading the book and enjoying it. He told me that he had read a bunch of Repairman Jack books, and mentioned that there were some 'other' elements in them--meaning occult or supernatural. I'm not a huge occult or supernatural book fan, but after finishing Cold City I picked up The Tomb, and really enjoyed that. From then it was one Repairman Jack book after another until I finished the entire series more or less in order. I really enjoyed Nightworld. It really is well written horror in the descriptions of some of the things happening to some of the characters in it really evokes a sense of--well, horror (it's late and I can't think of a better description). I finished the entire Repairman Jack Series in about 3-4 months. I consistantly ahd trouble putting the books down.
Anyway, after finishing the Repairman Jack Series I went on to read The Keep, Reborn (which I put down with a few hundred pages left to go and will go back to), and then picked up the Secret Histories, which I am working my way through now.
I really marvel at the way FPW created a whole mythology that ties together these and some of his other books, and the whole concept of a secret history of the world and otherness.