Homepage image: Spanish poster for Fellini's slacker film 'I Vitelloni'

THIRTYSOMETHING, THE 1980s TELEVISION SHOW that helped define the boomer experience, was about wanting youth despite its terror. The suffix playfully captured the confusion of growing up and old and recognized — the big difference between 31 and 39.

Robin Marantz Henig and Samantha Henig’s new book on the state of young people today, Twentysomething: Why Do Young Adults Seem Stuck?, appears, at least in name, to be a nod to the show. But the authors never mention the connection, and the “something” lumps together the people at each end and in between and interrogates their state of being “stuck.” Twentysomethings, they write, seem unable to attain the traditional markers of adulthood — finishing school, moving out, becoming financially independent, marrying, and having children — by the time they turn 30 because of an excess of choice, privilege, and ego.

The Henigs may have the ideal pedigree to write such a book. They are mother and daughter, boomer and millennial, former New York Times magazine writer and present New York Times web editor. The reflection on mom losing her job while daughter wins one — at the hands of the same editor — is fascinating, and particularly illuminating of the authors’ relationship, their experiences of aging, and their relatively elite status, which the younger Henig, capturing a clear shift in generational style and thinking without commenting on it, takes particular time to acknowledge. But the format they choose — each chapter divided into “now is new” and “same as it ever was,” with Mama Henig writing most of the text and Daughter Henig interrupting in italics — makes for more pleasant, dinner-table debate than the stuff of polemical generation-defining tomes. As such, Twentysomething is more interested in the flashiest of phenomena that make this generation different — the Internet, and the neuroscience that aims to observe the Net’s impact on our minds — than with the demographic, economic, and social changes that have rumbled unglamorously along for several generations to come to a head as the millennials hit adulthood: globalization and deregulation; professionalization and diversification of careers; immigration and the assimilation of racial minorities; and gender equality and the apparently dreaded, never-mentioned f-word, feminism.

The Henigs acknowledge the trickiness of generational defining and grouping in the introduction. The last of the baby boomers were born far too late to have participated in that group’s supposedly defining moment, the Vietnam War. Even earlier, some members of the so-called interbellum generation, born in the early 1900s and named for being too young to serve in World War I and too old for World War II, still fought alongside the Greatest Generation. The people named Generation Y were born between 1977 and 1995 to boomer parents. (There may be nothing worse for a generation attempting to distinguish itself than to be named after the slacker generation before it.) The oldest grew up Internet-less, afraid of nuclear weapons, and believing that diversity meant one super-cute black child in a room of white kids and feminism meant sneakers with power suits. The youngest of Gen Y probably can’t recall a life offline, feared terrorists, watched Barack Obama take the st...