There was a pretty meaty article in the Washington Post recently that discusses the novel, and the movie, with much more detail than I was intended to do here—replete with author commentary. So let me just quote some of that, and point you to the rest of it, if you're interested. It's worth a read even if you have only a casual interest in Jesse James (registration required).
It's really a story about fame, mythology, and the cold-blooded truth. And Hollywood. I was really curious to know how Hansen's novel, which came out quite a long time ago and was not widely known, all of a sudden made it to the big screen. Well, of course, it happened just the way you imagine it happening with your novel:
A filmmaker walks into a used bookstore.Hansen offers some fascinating insights from his own James research, the sources he used, how he tried to retain historic authenticity around characterization. How, all these years later, out of the blue, his phone rang. "Something about Brad Pitt."
Australian filmmaker Andrew Dominik was in Melbourne, hanging out with friend Rowland Howard, the Australian rock musician, when they strolled into a second-hand bookstore three years ago. Howard picked up a title, started reading it, then stopped. "He said, 'Wow, this would make a good movie,' and he handed me the book," recalls Dominik. It was Hansen's The Assassination of Jesse James by the Coward Robert Ford. Dominik purchased the book, left the bookstore, and started reading. "It knocked me out."
His latest film project had collapsed. He needed work. So he phoned his agent in California. "My agent said, 'Jesse James? Oh, I can sell that. Jesse James is like Batman.'
Already the London TimesOnline has weighed in with a review of sorts: "It's 1881 and when Brad Pitt swaggers into view, dressed from head to toe in black, we know we are in the presence of a superior bastard. The star of The Assassination of Jesse James by the Coward Robert Ford is a member of the James Gang and one of America’s most ambivalent myths."
Good enough for me.