In 1959, the writer John Howard Griffin undertook the ultimate experiment in immersion journalism. A white Texan, he dyed his skin in order to spend a year as a black man in the segregated Deep South. The book that resulted, “Black Like Me,” justified Griffin’s deception, and raised it above the level of a stunt, because its discoveries could have been made in no other way. The point of Griffin’s experiment was not just to obtain information but to shock the conscience of his white readers, by forcing them to undergo the sudden social demotion that came with a change in skin color. When he wrote about the “hate stare” that whites habitually gave blacks, about the petty humiliations and physical threats he constantly encountered, Griffin made those evils come home to white readers, in a way that no black writer could have. He wrote not just as a spy but as a sacrificial victim, suffering the pain that most whites refused to acknowledge, much less share.

When you first open Norah Vincent’s new book, “Self-Made Man” (Viking, 304 pages, $24.95), it is hard to shake the ghost of “Black Like Me.” Explicitly claiming to follow “in the tradition of John Howard Griffin,” “Self-Made Man” records the results of a superficially similar experiment. Over a year and a half, Ms. Vincent, a widely published journalist and pundit on issues of sexuality and gender, regularly disguised herself as a man in order to infiltrate male environments and try on masculine roles. Disguised in a beard, men’s clothes, and 15 pounds of added muscle, Ms. Vincent became “Ned,” who freely entered zones where Norah would not have been welcome: a men’s bowling league, a Catholic monastery, a low-rent strip club. In these and other places, Ms. Vincent was able to observe the reality of what Hemingway called “Men Without Women.”

That reality, as any man could confirm and most women might guess, is often far from savory. In fact, Ms. Vincent’s elaborate infiltration often seems superfluous, simply because the truth about male grossness is no secret. Here, for example, is Ivan, a door-to-door salesman at a bargain basement, Glengarry Glen Ross-type firm where Ned is briefly employed: “‘Now that chick over there,’ resumed Ivan, pointing to a tall, skinny blonde in mules and a miniskirt, ‘she’s eighteen and pregnant, and all she wants to do is f–. My one goal for the day is to do her tonight.'” Then there is Phil, who introduces Ned to a sordid strip club: “‘What are most guys looking for in a woman? We’re not looking for a nice person. We’re not looking for someone to rear our children. …We’re looking for someone we can stick our d–s into all the time. That’s ninety-five percent of looking for a woman.'”

If this kind of ugly bravado were typical of what Ned encountered, “Self-Made Man” might have turned into a “Black Like Me” for the post feminist age. But the gender divide, Ms. Vincent recognizes, is not really comparable to the racial divide, and the injustices men do to women are not as easily understood as those that the civil rights movement sought to remedy. While whites and blacks can be, and to some extent still are, genuinely segregated, men and women are never strangers; their destinies are linked by the deepest kinds of need, their responses to one another are always dialectical.

Ivan blusters about preying on a pregnant teenager, Ms. Vincent shows, but the intended target simply walks away, leaving him with no resource except more bluster, declaring that she was only worthy of oral sex, “nothing more.” Phil, it turns out, is a married man with two daughters, and never gets closer to Don Juan-hood than watching strippers. Ms. Vincent’s greatest strength as an undercover reporter is her ability not to be blinded by the smokescreens of machismo, but to see through them to the great male truth: that “know-it-all insouciance … betrayed exactly how much, not how little, women and the esteem of women actually meant.”

In other settings, Ms. Vincent discovers other forms of male posturing. When Ned joins a bowling league, she finds a group of close friends who barely ever talk about their lives, problems, or feelings. When one member of the group learns that his wife is dying of cancer, he lets the news drop in a few gruff sentences, expecting and receiving no shows of compassion.

The same emotional stoicism turns up, more surprisingly, in a Catholic monastery, where any show of affection between monks is quickly derided as self-indulgence or latent homosexuality. The one man in the monastery whom all the monks despise, Ms. Vincent writes, is a Brother Crispin, who let it be known that he is taking an anti-depressant medication. Such softness provokes a contempt that is really a form of panic: Crispin “was the fat kid on the playground, the hated projection of everybody’s hidden weaknesses, the shivering manifestation of failed masculinity on display.”

Far from a Griffin-like expose of social oppression, then, Ms. Vincent has actually written a diagnosis of the ailments of contemporary masculinity, in the tradition of Susan Faludi’s “Stiffed: The Betrayal of the American Man.” Her male disguise, though it is the book’s selling point and makes for some lively episodes, was probably not necessary for Ms. Vincent to reach her sane and compassionate conclusion: that being a man today is not a privilege, whatever it might have been in the past.

Thanks to the success of women’s and gay liberation, which Ms. Vincent never takes for granted, the most overt and institutional kinds of gender bias are now usually unacceptable, if not completely abolished. As a result, Ms. Vincent virtually never discovers a male arrogance or abusiveness comparable to the white arrogance Griffin saw everywhere. “White manhood in America,” she writes, “isn’t the standard anymore by which women and all other minorities are being measured and found wanting, or at least it doesn’t feel that way from the inside. It’s just another set of marching orders, another stereotype to inhabit.”

Rather, manhood today, she finds, is a volatile mixture of strength and weakness, aggression and deprivation. And its first, though not its only, victims are men themselves, made to play a role they neither choose nor understand. As a woman and a lesbian, Ms. Vincent belongs to two groups usually thought of as disadvantaged in comparison to men. “At the beginning of the project,” she writes, “I remember thinking that living as a man and having access to a man’s world would be like gaining admission to the big auditorium for the main event after having spent my life watching the proceedings from a video monitor on the lawn outside.”

When it’s all over, however, she concludes that she is “fortunate, proud, free and glad in every way to be a woman.” It is this confidence and compassion, even more than her derringdo, that make Ms. Vincent such a good secret agent in the gender wars.