The Big Sleep, like most of Chandler's novels, was written by what he called "cannibalizing" his short stories. Chandler would take stories he had already published in the pulp magazine Black Mask and rework them into a coherent novel. For The Big Sleep, the two main stories that form the core of the novel are "Killer in the Rain" (published in 1935) and "The Curtain" (published in 1936). Although the stories were independent and shared no characters, they had some similarities that made it logical to combine them. In both stories there is a powerful father who is distressed by his wayward daughter. Chandler merged the two fathers into a new character and did the same for the two daughters, resulting in General Sternwood and his wild daughter Carmen. Chandler also borrowed small parts of two other stories, "Finger Man" and "Mandarin's Jade".
As might be expected, all this cannibalising—especially in a time when cutting and pasting was done by cutting and pasting paper—sometimes produced a plot with a few loose ends. The famously unanswered question in The Big Sleep is who killed the chauffeur. When Howard Hawks filmed the novel, his writing team was perplexed by that question, in response to which Chandler replied that he had no idea. This exemplifies a difference between Chandler's style of crime fiction and that of previous authors. To Chandler, plot was less important than atmosphere and characterisation. An ending that answered every question while neatly tying every plot thread mattered less to Chandler than interesting characters with believable behaviour.
When Chandler merged his stories into a novel, he spent more effort on expanding descriptions of people, places, and Marlowe's thinking than getting every detail of the plot perfectly consistent. In "The Curtain", the description of Mrs. O'Mara's room is just enough to establish the setting: "This room had a white carpet from wall to wall. Ivory drapes of immense height lay tumbled casually on the white carpet inside the many windows. The windows stared towards the dark foot-hills, and the air beyond the glass was dark too. It hadn't started to rain yet, there was a feeling of pressure in the atmosphere." In The Big Sleep, Chandler expanded this description of the room and used new detail (e.g., the contrast of white and "bled out", the coming rain) to foreshadow the fact that Mrs. Regan (Mrs. O'Mara in the original story) is covering up the murder of her husband by her sister and that the coming rainstorm will bring more deaths: "The room was too big, the ceiling was too high, the doors were too tall, and the white carpet that went from wall to wall looked like a fresh fall of snow at Lake Arrowhead. There were full-length mirrors and crystal doodads all over the place. The ivory furniture had chromium on it, and the enormous ivory drapes lay tumbled on the white carpet a yard from the windows. The white made the ivory look dirty and the ivory made the white look bled out. The windows stared towards the darkening foothills. It was going to rain soon. There was pressure in the air already."
Of the historical plausibility of Geiger's character, Jay A. Gertzman wrote:
"Erotica dealers with experience had to be tough, although not necessarily predatory, and the business was not for the timid or scrupulous. But the criminality of erotica dealers did not extend beyond bookselling into organized racketeering; Al Capone and Meyer Lansky were not role models. A figure like A. G. Geiger, the dirty-books racketeer in Raymond Chandler's Big Sleep (1939) who supplements his business activities as owner of a pornographic lending library in Hollywood by arranging sex orgies and blackmailing rich customers, is a fascinating but lurid exaggeration. However susceptible film personalities were to blackmail, it was not the métier of book dealers."