Interesting info, Uncle Roger. I also had no idea SaMK fans have conventions. But I do remember that the show was very popular on CBS when it was on and the only reason it ended with its 4th season was because both Kate Jackson and Bruce Boxleitner wanted the series to go out while it was still successful. I also remember that Kate Jackson herself was a successful commodity for CBS because all her made-for-TV movies for the network brought in high ratings. After SaMK CBS wanted to do another series with her but things never worked out.
As for nowadays, the show seems to have a fairly large presence online. I've also noticed through the years that all sorts of SaMH merchandise is a frequent seller on eBay. And I just saw that the show has a 90% rating on Google. So it would seem like there is a market for that book...