From James Ellroy wiki--

Dialogue and narration in Ellroy novels often consists of a "heightened pastiche of jazz slang, cop patois, creative profanity and drug vernacular" with a particular use of period-appropriate slang.[34] He often employs a sort of telegraphese (stripped-down, staccato-like sentence structures), a style that reaches its apex in The Cold Six Thousand. Ellroy describes it as a "direct, shorter-rather-than-longer sentence style that's declarative and ugly and right there, punching you in the nards."[31] This signature style is not the result of a conscious experimentation but of chance and came about when he was asked by his editor to shorten his novel L.A. Confidential by more than one hundred pages. Rather than removing any subplots, Ellroy abbreviated the novel by cutting every unnecessary word from every sentence, creating a unique style of prose.[28] While each sentence on its own is simple, the cumulative effect is a dense, baroque style.[34]