Leading up to a 75th anniversary theatrical viewing of The Maltese Falcon, I've been re-watching Huston's classic adaption and re-reading Hammett's novel. It remains a favorite, though I see through different eyes now that I'm about the age of Spade's ill-fated partner, Miles Archer, than I did when I read and watched it repeatedly as a bookish pre-teen who had just discovered film noir and the novels of Hammett and Chandler.
In the film, it's not clear what book Spade has at his bedside under the alarm clock and which Gutman enjoys later while they await Effie's delivery of the bundle. We know from the novel it's Duke's Celebrated Criminal Cases of America.
We know from the Flitcraft tale that Spade worked for a detective agency in Seattle before coming to San Francisco, and that he's been partners with Archer for less than a year when he tells Effie he would sought to dissolve their partnership once their year contract was up. So, it tells us something that he's not just getting his information about the SFPD from experience, but that he's studying their history. Spade isn't only hard-boiled, he's well-read.
As an aside, he references Arnold Rothstein when discussing the case in the DA's office. I had always assumed that was a case from the book, but that's because my Tammany Hall and Black Sox scandal knowledge is somewhat and shamefully deficient. Also, because I haven't been watching Boardwalk Empire. Rothstein was prominent New Jersey underworld figure who was shot to death during a poker game over failing to pay a debt. So Spade's observation that the DA has Rothstein on the brain while investigating Thursby is an astute one. (Rothstein was murdered in 1928, a year before Hammett started publishing The Maltese Falcon in Black Mask magazine. Timely for the story, but a reference that probably would have been stale by 1941.)