The Ngram embedded above compares the popularity of four Golden Age of Detective Fiction Mainstays: Agatha Christie, Dorothy Sayers, Raymond Chandler and Dashiell Hammett
The Thin Man (1934)
by Dashiell Hammett
The above Ngram has no surprises. Agatha Christie, with her huge general audience, is first by a mile. Raymond Chandler and Dashiell Hammett both peaked in the mid 1980s, and Dorothy Sayers has remained flat since her glory days in the 1940s. The Ngram chart for Raymond Chandler and Dashiell Hammett probably reflects the ongoing canonization process in the United States, with a growth of secondary literature "filling up" during the 1980s and thereafter diminishing as there remains less to be said.
Chandler's rebound since the early 1990s (vs. Hammett's flat line) probably reflects a revival of popular interest in Chandler as the true literary stylist of Detective fiction. If you are looking for a point to distinguish between the collected work of Chandler and Hammett, The Thin Man, Hammett's succesful gentleman detective whose exploits were taken over by Hollywood, would be that point.
Read back to back with Dorothy Sayers Lord Peter Wimsey gentleman Detective, it is hard not to draw a firm conclusion that Nick and Nora Charles were his attempt to move up in the market, and perhaps a calculated move to sell books. There is no shame in that game by the standards of pulp fiction, but it is a literature no-no. Rampant success aside, The Thin Man degrades Hammett's authenticity in comparison to that of Chandler, who has no similar work.
Another facet that jumps out about the Ngram is that Raymond Chandler started later and lower than the other three. He remains in last place until 1960, when he passed Hammett (and stays more popular than Hammett from then on.) The Thin Man was Hammett's last novel, although he didn't die until 1961 he didn't really write much between 1934 and his death, and no more novels. Thus, the corpus of Hammett full length novels stops at five. The only one not to make the 1001 Books project is The Dain Curse (1929).
The Glass Key (1931), with its plot of urban politics, is the densest of the four. The Maltese Falcon(1930) is the most enduring in terms of a general audience, likely because the film is such a classic. However, I would recommend the other book- Red Harvest, which involves activity in a far Western mining town. For me, Red Harvest was the most memorable- only because I've seen the film version of Maltese Falcon so many times that reading the underlying book felt duplicative. Another appealing aspect of Red Harvest is that it stars his early, anonymous Detective "The Continental Op" and this use of the nameless protagonist almost seems like high literary modernism rather than a pulp fiction derived convention or lack of imagination.