One had to relive eighth grade. Another grew a beard so long and unruly it became more famous than its wearer. Yet another got to meet Richard Simmons on a cruise ship and was ranted at by a whole raft of motivational speakers.

They’re not professional pranksters, exactly, but the authors of what might be called gimmick books -- memoirs with premises so high-concept they could come from Hollywood pitch meetings: This year, I will take all of my instruction from self-help gurus. Or, this month, I will be radically honest with everyone I meet. Or, today I will try to behave exactly like George Washington, genteel bow, Dudley Do-Right walk and all.

The last few years have also seen many green-themed gimmick books, including Colin Beavan’s new “No Impact Man: The Adventures of a Guilty Liberal Who Attempts to Save the Planet and the Discoveries He Makes About Himself and Our Way of Life in the Process.” Gimmicky or not, some have been fabulously successful, and as it gets harder to break into print, the category remains one that publishers invest in.

“The difference between an organizing principle and a gimmick is a very thin line,” says veteran publishing observer Sara Nelson. “Most books need an organizing principle -- memoirs, especially: It makes the writing and reading of the book easier and more enjoyable. When that principle is so rigidly constructed, the reader can feel it’s not authentic.”

The king of the Gimmick Book is Esquire magazine writer A.J. Jacobs. The title of his forthcoming book -- “The Guinea Pig Diaries: My Life as an Experiment” -- gets at his approach. The New York-based Jacobs, whose nasally voice has been compared to Arnold Horshack’s from “Welcome Back, Kotter,” swears he’s not a cynical opportunist.

“The key is that the topic has to be fascinating to me,” said Jacobs, 41. “I have to have real passion. I am a writer and this is what I do, so it has to be interesting to readers. But it has to have stakes for me.”

Whatever the motivation, Jacobs’ new book seems essentially comic. By contrast, Robin Hemley kicks off his recent book with quotes from Hans Christian Andersen and Walter Benjamin. They’re pretty heavy names to invoke for a book -- entitled “Do Over!” -- in which a 48-year-old man relives kindergarten and summer camp, and even attends prom. But he’s after something serious.

“Everyone has regrets from childhood they’d like to reexamine,” Hemley says. “I wasn’t trying to change the past, but to change my sense of it.”

Five decades ago, George Plimpton suited up with the Detroit Lions and went a few rounds with light-heavyweight champ Archie Moore. In books like “Paper Lion: Confessions of a Last-String Quarterback,” from 1966, he helped establish what some call “participatory journalism.” He’s also one of Jacobs’ literary idols.

“I’m not a big athlete, so I never went that route,” he says. “What interests me is social interaction, knowledge and religion, so I try to adapt Plimpton’s method. It’s not physically demanding -- I’m not going to get punched in the face -- but it can be socially dangerous and intellectually dangerous. It can ruin my life in other ways.”

Jacobs scored hits with “The Know-It-All: One Man’s Humble Quest to Become the Smartest Person in the World” and “The Year of Living Biblically: One Man’s Humble Quest to Follow the Bible as Literally as Possible.” The first book, from 2004, had him reading the entire Encyclopedia Britannica, while the second, published in 2007, required him to purge his wardrobe of mixed fabrics, refrain from touching women (including his wife) during menstruation and to stone adulterers. In the new book, he experiments with “radical honesty” -- which involves, among other things, insulting his mother-in-law over a gift and telling a business associate that he was hoping to get her into bed.

The revival of Plimpton-like stunts may come from a dynamic in publishing: The contemporary memoir -- with its stew of drug abuse, incest, abject poverty and mental illness -- has become so grizzly that only the most harrowing childhood seems suitable for recounting.

“Poor Frank McCourt,” Nelson says, “wouldn’t get published today, I’d bet.” The dreary Irish childhood recounted in “Angela’s Ashes,” from 1996, “was pretty horrific, but in an old-fashioned way. Readers have been desensitized to that.”

Hemley thinks part of the durability of the high-concept genre comes from the unmasking of drug-and-poverty memoirs -- by James Frey, Margaret B. Jones and others -- as fakes. “We’re hearing about all of these memoirs whose facts are contested,” he says. “Here’s a form that’s quite verifiable. I can verify anything that’s in here.”

Many high-concept projects see strong sales -- Jacobs’ books have sold more than half a million copies -- and continue to be successful: “Julie & Julia” (2005), in which a young woman aims to cook all of Julia Child’s classic recipes, became the basis for the recent hit Meryl Streep film.

But the movement certainly has its critics. In a now infamous New York Times Book Review assessment of “The Know-It-All,” Joe Queenan called Jacobs’ book “corny, juvenile, smug, tired” and Jacobs both “a jackass” and “a poor man’s Dave Barry; no, a bag person’s Dave Barry.” Steve Almond has dubbed the genre -- in a review of Beth Lisick’s “Helping Me Help Myself” -- “shtick lit.”

Sometimes, however, a shtick is not just a shtick. Nelson aimed to give her own 2003 book, “So Many Books, So Little Time” -- in which she read a book a week -- “a narrative flow,” to make it “like a novel, where the character goes somewhere.”

Says Hemley: “If there is a serious center, some emotional power, to the book . . . it’s much more than a stunt. It’s something I call the ‘immersion memoir,’ going a bit outside yourself, using the outside world as a catalyst.” He praises Barbara Ehrenreich’s maid-chronicle “Nickel and Dimed” and Ted Conover’s “Newjack: Guarding Sing Sing.”

Still, how long can publishers support this combination of stunt journalism and personal exposure?

Jacobs jokes that the genre could experience the same kind of escalation that the grisly-childhood memoir went through: “I’ll have to die and go into the afterlife, and write about heaven or hell -- whichever one is more interesting.”

Every trend, after all, fades out. “This cycle has to end somewhere too,” Nelson says. “I don’t know what will come next. What happens in publishing is, ‘This worked, let’s do more of this.’ Then, it’s ‘That’s so five seconds ago.’ ”

Jacobs himself hopes the Gimmick Book movement keeps rolling, at least long enough for his next book, in which he tries to become the world’s healthiest man.

“I feel lucky about being able to make a living this way,” Jacobs says. “It’s like going to school your whole life, getting crash courses on these really interesting topics. If I ever get bored, we’re in trouble.”

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