Approached by HarperCollins president Michael Morrison about creating his own publishing imprint, Dennis Lehane was excited. But the “Mystic River” author wanted autonomy. “I didn’t want anyone pressuring me to pick the ‘book of the moment,’ ” he says. “This [arrangement] is informal, in the best sense of the word. It’s painless.” The new imprint, Dennis Lehane Books, debuts next month with “The Cutting Season,” the second novel by Attica Locke, a former screenwriter whose first foray into fiction, “Black Water Rising,” was a favorite of many critics. Lehane says he chose the book because it appealed to him as a reader. “I want a lot of depth in the language, character structure, and I want a story,” he says, listing the likely criteria for future Dennis Lehane Book selections. “It’s what I swing for as a writer. . . . Books that I probably won’t choose? Oh, there’s probably not gonna be any sci-fi, chick lit, romance, or post-modern meta-fiction. That’s just stuff I don’t particularly read, to be honest.” Aside from doing a little press — Lehane will introduce Locke at Newtonville Books on Sept. 19 — there’s not a lot of heavy lifting involved in overseeing an imprint, and that’s good because Lehane’s got writing of his own to do. There’s a new novel, “Live by Night,” which comes out next month; the sequel, which he’s already working on; a screenplay based on his short story “Animal Rescue”; and a TV series for FX. About “Live by Night,” Lehane says: “It’s my gangster book. Since I was a little kid, it was my dream to write a gangster book, and this is it.” And, yes, the novel already has been optioned — by Leonardo DiCaprio, no less, who starred in the movie version of “Shutter Island.” “I’m back in the Leo business,” says Lehane.