Mr. Shepard wrote more than 55 plays (his last, “A Particle of Dread,” had its premiere in 2014), acted in more than 50 films and had more than a dozen roles on television. He was also the author of several prose works, including “Cruising Paradise” (1996), and the memoir “Motel Chronicles” (1982). Though he received critical acclaim almost from the beginning of his career, and his work has been staged throughout the world, he was never a mainstream commercial playwright.

Several writers who grew up studying Mr. Shepard’s works said that they were struck by his boldness. Christopher Shinn, whose plays include the Pulitzer finalist “Dying City,” said he was reminded of Mr. Shepard’s gifts as a writer while watching “Buried Child” Off Broadway last year.

“I felt the play pulsing with Sam Shepard’s unconscious, and I realized how rarely I feel that in the theater today,” Mr. Shinn said on Monday. “Sam always wrote from that place — a zone of trauma, mystery and grief. Whether the play was more mainstream or experimental in its conception, he took the big risk every time.”

In the relatively naturalistic “True West,” two brothers of opposite temperaments find themselves assuming the personality of the other. (John Malkovich and Gary Sinise made their names in the Steppenwolf Theater Company production; Philip Seymour Hoffman and John C. Reilly memorably traded off the parts in the 2000 Broadway revival.) Roles within families depicted onstage continually shift and dissolve, as in Mr. Shepard’s great “A Lie of the Mind” (1985), the title of which might serve for every play he wrote.

As for love between a man and a woman, Mr. Shepard, whose long relationship with the actress Jessica Lange cast an unwanted spotlight on his private life, described that as “terrible and impossible.” He later explained: “It’s impossible the way people enter into it feeling they’re going to be saved by the other one. And it seems like many, many times that quicksand happens in a relationship when you feel that somehow you can be saved.”

That point of view received its fullest and most rousingly theatrical incarnation in “Fool for Love,” a portrait of possibly incestuous bedmates who spend their lives running away from and toward each other as fast as they can. The play received its first Broadway production only two years ago, starring a ferocious Sam Rockwell and Nina Arianda, in roles embodied three decades earlier by Ed Harris and Kathy Baker.

“I loved Sam,” Mr. Harris said in a statement on Monday. “He has been a huge part of my life, who I am, and he will remain so.”