As a child, Natasha Gregson Wagner followed a succession of good-luck rituals every time her mother left the house. “I couldn’t go to sleep until all twenty or thirty of my stuffed animals were lined up in a row on my brass bed, my Barbies perfectly positioned in their Barbie Dream-House. As soon as I finished brushing my teeth and turned the bathroom lights off, I had to switch on my swan night-light. I prayed every night, ‘Now I lay me down to sleep,’ including a special prayer to God to please keep my mom safe,” she writes in her new memoir, “More Than Love.”

The mom, of course, was Natalie Wood, and the book, released in conjunction with a family-approved HBO documentary — and just in time for Mother’s Day — is at once a poignant look at a complicated relationship, a knowledgeable exercise in brand management, and a tantalizing foray into “What if?”

For it was 11-year-old Natasha who, in November 1981, begged her mother not to take that ill-fated boat trip to Catalina Island. We all know what happened: In the middle of the night, Wood tumbled to her death from the yacht she shared with husband Robert Wagner. According to the official explanation, she slipped and drowned while trying to reach the boat’s dinghy.

The case was closed, but the rumors were already in full churn. Why would a woman so fearful of open water leave the safety of her bed? Had she been having an affair with actor Christopher Walken, the only other passenger? Had her husband exploded in a jealous rage? Was Wood’s death a tragic accident or — cue the strangled whisper of your favorite true-crime announcer — foul play?

We speculated at the time — some of us still do — but relatively few of us gave a thought to the girl she left at home, the one whose superstitious rituals had failed to accomplish their purpose. “Losing my mother was the defining moment of my life,” she writes now. “No other event would ever again so sharply etch its mark upon my soul, or so completely color the way I navigate the world, or leave my heart quite as broken.”

To an outsider, Gregson Wagner’s childhood would have looked like a cocoon of Beverly Hills privilege. Fireplaces in every room. Towering piles of presents for birthdays. (When she turned 13, she got an Arabian horse.) There was a housekeeper and a driver and a handyman and two cooks. Ruth Gordon for a godmother, Elia Kazan hanging out by the pool, Laurence Olivier stopping by for dinner. And, this being Hollywood, a slew of recombinant DNA. Wood and Wagner married young, divorced, had children with other spouses, then remarried. Natasha’s biological father was British agent-producer Richard Gregson, but her daddy of the heart was stepfather Wagner, and her surrounding family was an “alphabet soup” of step- and half-relations.

How differently her mother came up in the world. The adored daughter of penniless Russian immigrants, she discovered at a very young age a talent for playing make-believe on camera and, urged on by her fiercely ambitious mother, took on such eye-catching juvenile parts as the Santa skeptic in “Miracle on 34th Street” before transitioning to adult roles with “Rebel Without a Cause” (still, in my mind, her best performance). Over the next quarter of a century, she worked hard and steadily. She had to. From middle school onward, she was her family’s sole breadwinner.

That pressure, as biographers like Gavin Lambert have already charted, left its own cracks in Wood’s psyche. On at least one occasion, she attempted suicide, and she sometimes drank more than her tiny frame could absorb. (Alcohol was reportedly one of the factors in her death.) She was gone from home as many nights as she was there, but as her daughter remembers it: “My mother was my mirror. When I saw myself reflected in her, it was a self that was bigger and better and brighter.”

Gregson Wagner is frank in discussing her own grief-tinctured coming-of-age struggles, including an ill-advised first marriage to a philandering screenwriter. She also devotes a modicum of space to her “deliberately low-profile” acting career, which flourished in 1990s indie flicks like “Two Girls and a Guy” and “Another Day in Paradise.” That career seems to have given way now to parenting her own daughter and to curating her mother’s legacy — a gig that, between the 2016 coffee-table photo album (“Natalie Wood: Reflections on a Legendary Life”) the gardenia fragrance named Natalie, and the HBO documentary, is starting to look like a full-time job.

Understandably, then, our author is quick to douse the conspiracy embers that still swirl around her mother’s death (many of them fanned by Wood’s sister, Lana). “The circumstances of exactly how Natalie Wood ended up in the water will never be clearly established because she was alone when she died. And so I focus on the things I do know, that as certain as I am that the earth is round, my father [i.e., Wagner] would never have harmed my mother or failed to save her if he knew she was in danger.”

Give all due credit to the author’s sincerity and loyalty, but don’t ignore the imperatives of image control. And marvel that, four decades after Wood’s death, her brand is still selling, and she herself is still hard at work.

Louis Bayard is a novelist and reviewer whose most recent book is “Courting Mr. Lincoln.”

MORE THAN LOVE: An Intimate Portrait of My Mother, Natalie Wood

By Natasha Gregson Wagner

Scribner. 304 pp. $28