Griffin Dunne’s family has done so many larger-than-life, unbelievable things that when the actor-director-producer started to write his memoir “The Friday Afternoon Club: A Memoir of Family,” he realized it wasn’t enough to start the story with his complex writer father Dominick Dunne.

In fact, it was impossible to understand the forces that shaped the Dunnes, including his uncle John Gregory Dunne and sister Dominique Dunne — without understanding his father’s abusive upbringing in an Irish Catholic family, his mother’s Mexican heritage and all great love stories, clandestine affairs, celebrity encounters and tragedies that seem to surround them, buffeted with lots of pitch-black mordant humor.

The heart of the new memoir is the 1982 murder of Griffin Dunne’s younger sister, “Poltergeist” star Dominique Dunne. It’s the first time he’s really grappled with telling the story of that pivotal event in his family’s history. The...