“Fortunate the young man who does not make his entrance into too wide a world” — so observed Randolph Bourne in “Youth and Life,” one of the loveliest essays ever written about one’s first 25 years, that period before the onset of old age and obsolescence. Bourne wrote this in 1913, and his intention was to aid the youth in managing their energies as they embarked on the ready-made quest “to be everything, do everything and have everything.” This is a familiar tension, our tendency to protect and caution the young, all the while envying in secret their freedom from responsibility and wide-open futures. For Bourne, Henry Adams, and many others who wrote eloquently about being young in America, salvation was found in experience, in doing and mastering, and in the steadfast conviction that the world could be reshaped according to new ideas.

But none of them ever had to deal with the Internet. Few of them could fathom the onset of something called “youth culture.” And even the 20th century’s first great prodigy, Walter Lippman, whose undergraduate essays inspired the philosopher William James to trek across Harvard Yard and seek him out for conversation, would cower at the idea of competitive spelling. In the parlance of Bourne: Fortunate, too, the young man who has no idea how to work Google Alerts.

Being young in the 21st century may not be harder than in earlier times, but it certainly gives us more opportunities to make our lives harder than they need to be. The three vaguely idealistic, 20-something, college-educated men at the center of “All the Sad Young Literary Men” (Viking, 256 pages, $24.95), the debut novel by Keith Gessen, do not spill forth with energy. There is no risk of flaming out like one of Bourne’s youthful radicals. Instead there is passivity. An omnipresent anxiety that one’s moment for greatness or fame — “the anti-death,” as one character calls it — is slowly, helplessly passing. It is the twilight of promise, when the only sensible thing to do is get a real job and join the masses who are “becoming lawyers and getting married, getting married and becoming lawyers.”

The novel opens with a romantic vision of the eternal post-collegiate: “To be poor in New York was humiliating, a little, but to be young — to be young was divine.” It is a vision that presumes that life will only get better. Mr. Gessen’s young men — an erstwhile scholar (Mark, a graduate student), a journalist (Keith, a freelancer), and a novelist (Sam, a skilled self-Googler) — imagine themselves ascending to positions of world-historical importance, but they rarely act beyond their own self-absorptions. They are hung up on their predecessors, so much so that it distracts them from the hard work at hand. And so they drink beer, go to the gym, and check their e-mail — a lot — too much, some might say. Their lives chart a sine wave, one moment lazy and the next irrationally, improbably, senselessly busy.

Most of all, they inhabit a world of future promise, constantly measuring themselves against anyone and everyone rather than doing whatever it is they are supposed to be doing. Sam sits in a Cambridge café, ready to get started on his novel, but his mind wanders: “The living writers of the world were Sam’s enemies, Sam’s nemeses. Sam was once a living writer himself, even better than a living writer, a future writer — there’d been a picture of Sam in one of those publisher’s catalogs.” Unfolding his notebook — his “notes toward greatness” — he works instead on a list of women he has seen naked, steeled by the realization that Emerson’s notebooks probably didn’t seem so important long ago either. Mark casts his neuroses-rich graduate student life against the struggles of Bolshevism and Menshevism, and wonders why he is “always ending up like Liebknecht” — an obscure but resonant figure from his dissertation research. Keith is the most endearing of the trio, a sensitive writer dreaming of meeting his favorite essayist, who would “know right away how different I was.”

Youth is a durable theme, but it requires a careful hand to make the plight of the young and privileged seem remotely compelling. For Mr. Gessen, this task is further complicated by a rough sense of how the story ends. His characters are essentially versions of Mr. Gessen and his real-world friends, the co-founders of the cultural journal n+1 — two of them share the same names, the dates and sites of schooling seem to fit, and the vague yet strident sense of self-regarding ambition certainly fits. Perhaps this is why the three characters are so ill-defined, occasionally indistinguishable in thought, action, sense of humor, and in the troubled ways in which they deal with women.

Still, there is something weirdly fetching about “All the Sad Young Literary Men” — weird because the book describes such a tiny, occasionally infuriating world, one where progressive magazines and book reviews might save the world and crossing paths with the vice president’s daughter is just a part of a Harvard education. It is a world of less-than-practical professions. And yet there is something affecting about the impossibly great aspirations shared by Mr. Gessen’s trio, especially as it shields them from thinking too deeply about the cowardly deeds that pock their day-to-day lives. Mr. Gessen describes something very true, this condition of being smart and good-hearted yet paralyzed to move forward in life. In principle, the idea of meritocracy grants us all a chance at greatness, but how do we know when to surrender? To whom do we address our supposed genius, our blueprints for rebuilding the nation? Modern life grants us infinite choices — and this can be deeply crippling. As the novel meanders toward our semi-awful present, Sam, Mark, and Keith relinquish a tiny bit of their self-regard, and return to the hard work of remaking the world in their own image. There is a difference between terminal immaturity and refusing to grow old.

Mr. Hsu teaches English at Vassar College.