EMMANUEL DUNAND/AFP/Getty Images Bristol Palin holds hands with boyfriend Levi Johnston during the Republican National Convention at the Xcel Energy Center in St. Paul, Minnesota, on September 3, 2008

It should go without saying that envy over your mother’s pregnancy is never a good reason to get knocked up yourself. But that’s what motivated Bristol Palin, writes her ex-boyfriend, Levi Johnston, in his blithely named memoir, Deer in the Headlights: My Life in Sarah Palin’s Crosshairs, which comes out Tuesday.

Johnston writes that Bristol was so peeved that her mother, former Alaska Gov. and will-she-won’t-she presidential contender Sarah Palin, was expecting a son that she finagled a way to get preggers too, at 17, with her very own baby boy — and with Johnston, now 21, as her allegedly oblivious co-conspirator, according to the Associated Press, which tracked down a copy of the book last week.

“Let’s get pregnant,” Bristol urged him in March 2008, according to Johnston, who says he was “too dumb” to use contraception; having a baby of her own was exactly “what she wanted,” he writes. Tripp was born in December 2008.

The book was inspired by Johnston’s desire to fess up and “tell the truth about my close relationship with the Palins,” he said in a statement released by his publisher several months ago. “My sense of Sarah and my perplexing fall from grace — how I feel and what I’ve learned. I’m doing this for me, for my boy Tripp and for the country.”

Avid followers of the now-defunct Bristol-Levi duo may be totally flummoxed, wondering what to believe, particularly since Johnston’s recollection of their time together varies considerably from the memories that Bristol ponied up in her own book, Not Afraid of Life: My Journey So Far, which came out in June.

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While she shares that she first had sex with Johnston on a wine cooler-infused camping trip, he says that she lost her virginity to him long before that, although at least one camping trip did indeed take place, judging by this poetic passage from Johnston that describes his ardor for Bristol:

She was the sun of my life. We became secret camping lovers, scraping gnarly gnats off our lips before we kissed.

He also insists he was present for Tripp’s birth, despite Palin family denials to the contrary. Who’s telling the truth here? Or, perhaps the better question is, who cares?

The very idea of two 20-somethings penning memoirs is in itself an insult to the genre. The fact that the memoirs are fueled largely by he-said-she-said versions of who had teen sex and when amounts to a whole bunch of TMI.

I won’t be buying Johnston’s book, though it’s certain that others will. Celebrity dads — and moms — are the ticket to media sales, if Parenting magazine’s recent move to put famous parents instead of anonymous cute kids on the cover is any indication.

Perhaps Tripp, nearly 3, will be the next cover model?

Bonnie Rochman is a reporter at TIME. Find her on Twitter at @brochman. You can also continue the discussion on TIME‘s Facebook page and on Twitter at @TIME.