Roxanne Roberts is a reporter for The Washington Post’s Style section.

Paul was converted on the road to Damascus. Gloria Steinem saw the light on the road to Toledo. Or New Delhi. Or was it Houston?

In “My Life on the Road,” her first book in more than two decades, the 81-year-old feminist leader takes a trip down memory lane: the journeys, traveling companions and detours in a lifetime of activism. At each stop she learned something profound, something moving, something that filled her with resolve to keep fighting the good fight — all lovingly reconstructed in 250 pages.

That’s great news for Steinem fans and future biographers: The book is a travel diary of the women’s movement, a first-person account of Second Wave feminism. But if this is your first deep dive into her world, it’s a tsunami of earnestness that all but swamps readers with Life Lessons. I’m hanging on a limb here, but anyone who picks up a book by Gloria Steinem probably knows that men can still be chauvinists and women can still be treated unfairly. Duh and duh.

And therein lies the problem with this book. Like all apostles, she completely and passionately believes in her life’s mission. She is, in a word, relentless — a crucial trait for an activist; it’s less endearing for those who have to hear (or read) the drumbeat, over and over, even if they are already sympathetic to the cause.

My Life on the Road by Gloria Steinem ( Random House / )

Take what could have been a fun, or at the very least, interesting experience: Thanksgiving with your very rich boyfriend. Steinem is on a private jet with her unnamed date and four other couples, also very rich, headed for a long weekend in Palm Springs. Maybe, she thinks, she can convince them that it’s smart business to support health and anti-violence projects for girls and women. But there’s not much time for lobbying: They’re playing tennis or golf, she’s in a bungalow writing an overdue article.

On Thanksgiving Day, the group is invited to have dinner with Frank Sinatra. She tries to get his wife, Barbara, interested in donating to domestic abuse victims, without success. When the legendary singer finally shows up, Steinem notes only that his wife waits on him like a geisha and that he has an enormous collection of toy trains, which he proudly shows off.

Instead of being curious — “Hey, Frank, what’s with the trains?” — Steinem silently calculates the cost and thinks of all the ways the money could have been better spent. On the flight home, the men are talking mergers, and the women are talking about weight loss. Steinem tries once more to convince them that supporting women’s causes is good for business but is politely rebuffed. “I am an isolated island around which an ocean of talk flows,” she writes.

Or maybe she is just that person who never lets up, who’s not much interested in anything outside her specific universe, whom people politely avoid because she confuses social occasions for fundraising opportunities. The kind of person who makes history but isn’t much fun to be around.

To be fair, her early life wasn’t much fun. Her father was a happy-go-lucky traveling salesman; her mother depressed and mentally ill. The family traveled the country during the Depression, and she wasn’t enrolled in school until she was 11 years old, a history well-suited for a future as a social organizer. “It satisfies my addiction to freedom that came from my father, and my love of community that came from seeing the price my mother paid for having none,” she writes.

The roots of that rootlessness — with no children of her own, no desire for wealth and a late-in-life marriage — launched an unusual life for a woman in the 1950s: writing, organizing and activism. Despite, or because of, her striking looks and intellect, she became and remains the most recognizable face of the women’s movement.

It is an extraordinary life, one filled with encounters with amazing characters who speak in perfect sound bites and confirm that she’s on the right track. On a taxi ride to JFK Airport in the 1960s, Steinem is making out with her African American lover. Instead of condemning the couple, the driver tells them they remind him of his own marriage: “Me and my wife and you two, we’re what this country is all about.” Years later, while Steinem is campaigning for Hillary Clinton, a drunken critic of Hillary confides to her that the Clintons’ marriage “made her aware of how unequal hers was.”

It could have happened exactly like that, but after a few dozen stories like this I began to wonder if some things might have been exaggerated for dramatic purposes.

After a campus visit in Boston that goes past midnight, Steinem writes, she misses the last plane and takes a car service to New York because she is scheduled to leave on yet another trip in the morning. Her driver is a chatty former trucker who misses his old road buddies and invites the wide-awake Steinem to experience a real truck stop. She loves it so much that they stop at four more dives, where she bonds with female bartenders and drivers.

“I see Manhattan lights reflecting in the night sky, but I’ve lost all sense of time,” she writes. Me, too. Somehow she’s managed to squeeze in a four-hour drive and five eye-opening truck stops before dawn, discovering the gritty authenticity of this unseen world in just one night. Poetic? Sure. Poetic license? Maybe.

Or her encounter with a “very taciturn and masculine” college student in the Midwest who shares a heartbreaking tale of sexual abuse that Steinem repeats word for word from memory. “I wouldn’t say I was lucky,” he tells her, “but it would have been worse if I thought I had to control and abuse other people.” That may have been a verbatim account of his lengthy monologue (perhaps Steinem has perfect recall), but it reads like a tragic-yet-uplifting parable rather than an actual conversation.

This shape-shifting, her stream-of-raised-consciousness revelations, might work in a novel — there’s a nobility and fierceness to Steinem’s quest, the classical hero’s journey intertwined with her fascination with Native American history and culture. But as a memoir, it’s sanctimonious and curiously impersonal. There’s a lot about her fellow activists, but barely a mention of the people closest to her: her sister, who took Steinem in as a senior in high school so she could have a semblence of a normal teenage experience, her niece and nephews, her best friends.

And not a single word about her late husband, David Bale, a man she once said had “the greatest heart of anyone I’ve ever known.” Steinem was 66 when she married the South African businessman in 2000, and they had, by all accounts, a happy union until he died of brain cancer three years later. The omission seems especially odd because Bale (the father of actor Christian Bale) often accompanied Steinem on the road. “We discovered that he liked to travel with me, and after an event, he would have 500 young women around him, all so relieved to see that you can be a feminist and have a relationship with a man — and he was so excited by it,” she said in a 2011 interview with the Guardian.

It would have been interesting to learn more: how that relationship affected her life and work, what she learned off the road. But she literally says nothing about him or her marriage. Then again, spouses seldom make it into the history books, do they?

Instead, she dedicates the book to the late John Sharpe, the British doctor who performed an illegal abortion for Steinem in London in 1957, allowing her to embark on her lifelong journey instead of being a single mom at age 22. “You must promise me two things,” he told her. “First, you will not tell anyone my name. Second, you will do what you want to do with your life.”

Steinem’s position as an icon of the 20th-century feminist movement is unquestioned. But, in the end, “My Life on the Road” is a long, dusty pilgrimage best left to the faithful or the penitent. For the rest of us, it’s a tough slog.

My Life on the Road

By Gloria Steinem

Random House. 276 pp. $28