Anybody ever read Karl Alexander's novel?
Karl Alexander's novel came back into print around the time he published the sequel, Jaclyn The Ripper (which I haven't read yet).
From what I can gather, Nicholas Meyer was friends with Karl Alexander, read the then-unfinished novel and optioned it for a movie before it was even published. So although it did come out after the movie did, it wasn't technically a movie novelization.
It's quite interesting and goes quite a bit more into characters' backstories--most notably, Stephenson himself. It's revealed that he was a member of a "respectable", repressive family. Being not quite right from the get-go, he fell in love with (and slept with) his sister (yes, you read that right). But his sister revealed that he hadn't been her first--their father had. By consent. (Nice Victorian family, eh?) Stephenson tried to beat her to death, but his father intervened and beat the crap out of HIM. He only returned for his father's funeral; his brothers glommed onto the estate, his sister had left for God-knows-where a long time ago and his mother was raving mad (possibly from syphilis that the father had given her, but it's not stated). It was the sister's picture in the pocket watch, the sister's face he visualized whenever he was in the act with the prostitutes and when he slaughtered them.
There are also a few things that make a little more sense in the book: the 1893 police never positively identify Stephenson as the Ripper (as they seem to in the movie) and, of course, he's never brought back to answer for his crimes so it makes much more sense that the Ripper is never identified.
Also, there's the question of why Stephenson, after being pronounced dead in San Fran, turned up alive: he switched his records with an emphysema patient--and then turned off his oxygen machine.
All in all, it's a good read and I'd recommend it. You might find one or two things you'd wish could have made it into the movie.