Near the end of her memoir, Bristol Palin declares that her love story with Levi Johnston is “not unique” and places it in historical perspective for the reader. “Women throughout history have looked back at their relationships and wondered how they could’ve loved a man who treated them so badly,” she writes. “From Hillary Clinton to Sandra Bullock, from Jackie Kennedy to Jennifer Aniston, from Elin Woods to Princess Diana.”

Yes, however improbably, Palin just placed herself among a pantheon of scorned women that includes the secretary of state and the “Friends” actress who gave the world the “Rachel” haircut.

Not Afraid of Life” is a vent for her fury.

Palin and Johnston’s combustible relationship has been exciting the media ever since John McCain picked Palin’s mother as his running mate in the 2008 election. Now, at the age of 20, Palin has written a memoir about the ordeal of being Johnston’s partner, a teenage mother to their child and a contestant on “Dancing With the Stars.” (Johnston will, of course, release his own memoir later this summer.)

Johnston is called a “gnat” and a “big guy who had a talent for trash-talking but nothing else.” He’s “inarticulate,” “cocky” and “obnoxious.” He’s the bully who pulls hair, trips people and “put Ex-Lax in some kid’s brownie.” He lies to her all the time — about other girls, about having bought a new truck even though he was broke, about reeling in “twelve fish when he didn’t catch any.” Yet he hooked Palin.

“Like many women throughout history, I went for the ‘bad boy’ who didn’t care about authority,” she says. “Levi’s bad behavior wasn’t a deal breaker for me.” They had an on-again, off-again relationship from the moment they met in seventh grade that, according to Palin, was always being tested by his romps with other girls and her family’s disapproval of him.

She begins the book with their lowest moment together, promising that “No one has ever heard this part of my story” and that what we’re about to read “would affect my life in ways a teenager could not comprehend.”

What happened? One summer night in high school, Palin lies to her mom, saying she’s spending the night at her friend’s house. Instead, she goes camping with Johnston and some friends. She writes that she had never taken a sip of alcohol before the camping trip — “I knew nothing about anything bad really . . . especially the differences between vodka, beer, and whiskey” — but as she sits by the fire, she finds herself enjoying the way the wine coolers Johnston is plying her with make her feel “young and carefree.” The next thing Palin remembers is waking up in his tent with his empty sleeping bag by her side.

“What I don’t remember is what transpired between the moment when I was sitting there by the fire talking and the moment I awakened the next morning,” she writes. She goes on: “Suddenly, I wondered why it was called ‘losing your virginity,’ because it felt more like it had been stolen.”

Did something sinister take place in the woods? It’s not clear. Later, she softens the account by writing that she “barely remembered” the night. Then, two chapters after that, she says of the encounter, “We’d messed up.” So it was a mutual bad decision but the sex was consensual? This seems important. But whatever happened in the tent that night, they were soon in a sexual relationship.

Palin wrote this story so others can learn from the “pretty foolish decisions” she made, namely having sex before marriage. So it’s a detriment to her message that she never pauses long to consider her own struggle, and failure, with practicing abstinence. “Since Levi and I were going to get married, I rationalized that our premarital sex wasn’t that big of a deal,” about sums it up.

Palin’s self-deprecation is appealing (“my life had become a Jerry Springer episode, and a bad one at that”). Moreover, she writes convincingly, and humbly, of how she was able to move beyond her feelings of shame and Hester Prynne-like social ostracism. Palin could have lingered longer on other things that are really interesting, like her relationship with her mother, or why, beyond a vague hope that he would someday change, she stuck around with Johnston for so long. (If a guy, say Johnston, proposes by slipping a ring on your finger while you’re watching TV and the first words out of his mouth are, “It was expensive,” his heart is probably not in it.)

In the place of real insight, we frequently get catty asides. Some of her ex’s trash-talk expertise must have rubbed off on her, because she dishes it out with aplomb.

When she first met Meghan McCain, Palin “shook her hand and tucked away the sneaking suspicion that I might need to watch my back.” And on the night of her mother’s speech at the Republican National Convention, Palin says that Meghan “stormed” into the hair and makeup room demanding immediate attention. Unfortunately for McCain, Bristol and her sister Willow occupied the stylists’ two chairs. “Surely she wasn’t so self-obsessed that she believed everyone else should scoot over so she could take priority?”

The most head-scratching moment of the book occurs on its second-to-last page, where Palin tells us that a guy she offhandedly mentioned at the beginning had, for some reason, committed suicide. Somehow this is meant to demonstrate to us that everyone “wrestles with indignities, pain, and disappointments,” but, as her title insists, we shouldn’t be afraid of the challenges life throws at us. The comparison makes little sense and, whatever the intention, comes across as tactless.

If Palin truly counts herself among the most famous of women who have been wronged, and she really does want to help young adults avoid making similar mistakes, then it’s sad she couldn’t put her celebrity to more positive use.

Lowman is on the Book World staff. Michael Dirda will review a book Friday.