In his book Happiness, former Oxford don Theodore Zeldin provided a brilliant description of life in the modern academy: “To remain sane, scholars had to become willing prisoners in a tiny cell, because here at least they could lay down the law about some tiny fragment of truth, like the habits of the earwig or the foreign policy of medieval Zanzibar. a few ambitious ones might grow dissatisfied with being master, or mistress, of only a small domain, and they might build up… grand theories… applicable to other domains; and their imperialism kept the academic world simmering in permanent nervous conflict.”

Bob Putnam has certainly been the source of much nervous conflict among his scholarly peers. As the cover of his new book reminds us, he is author of Bowling Alone, sensible marketing, given that it was a social-science smash hit in 2000. Describing his own “grand theory” of a decline in “social capital” – the ties that bind communities together – Putnam escaped the narrow confines of his Harvard office to become a global public intellectual, presidential adviser and, for the New York Times, “poet laureate of civil society”.

Bowling Alone provoked deep academic debate and study, firmly placing the idea of social capital on the intellectual map. It influenced political discourse on both sides of the Atlantic. In the US, it had a direct impact on legislation, including the Serve America Act, as well as on the compilation of official statistics, with a host of new surveys capturing various dimensions of social capital and civic engagement. This new data fuelled a fresh round of research, further enhancing Putnam’s ideas.

In his new offering, Putnam tells a more nuanced but more troubling story. Combining rich qualitative interviews and sharply presented data, he describes a divide in social capital, rather than a simple decline. The top third of US society – whether defined by education or income – are investing more in family life, community networks and civic activities than their parents, while the bottom third are in retreat, as families fracture and both adults and children disengage from mainstream society.

This gap amounts, Putnam fears, to a “crisis” for the American dream of equal opportunity. Advantages pile up for the kids born to the right parents, all but guaranteeing their own success in life – in stark contrast to the fates of those struggling at the bottom. The difference between “haves” and “have-nots” was once economic. Differences in social trust, family life, parenting and community vitality were minimal. Now, though, the haves have it all.

Putnam presents dozens of “scissors graphs” showing the top pulling away from the bottom in relation to school sports, obesity, maternal employment, single parenthood, financial stress, college graduation, church attendance, friendship networks, college graduation and – revealing a small obsession of Putnam’s – family dinners. For him, their absence represents much of what is going wrong in America. Andrew, a second-year college student from an affluent white family in Bend, Oregon, says: “My dad and my mom have always made sure we eat dinner together. I actually learned a lot from those conversations.” Stephanie, a black single mother, says: “We’re not a sit-down-and-eat family… We ain’t got time for all that talking-about-our-day stuff.” For Putnam, family dinners act as an “indicator of the subtle but powerful investments that parents make in their kids (or fail to make)”.

The concatenation of advantages and disadvantages is visible in economic sorting at the neighbourhood level, leading to social sorting in terms of schools, churches and community groups. Putnam writes: “Our kids are increasingly growing up with kids like them who have parents like us.” This represents, he warns, “an incipient class apartheid”.

The use of “real life” examples is a depressing cliche of social science books. Scholars fool themselves that boring data can be camouflaged: “Meet Rita, who works in a diner, she is an example of…” Putnam avoids this trap. The interviews were conducted by his talented colleague Jennifer Silva, who has produced a fine book of her own, Coming Up Short, and provide valuable qualitative data on the state of the nation. A striking example is the haphazard way in which less-advantaged Americans become parents. Darleen got pregnant two months into a relationship with Joe, her boss at Pizza Hut. “It didn’t mean to happen,” she reports. “It just did. It was planned and kind of not planned.” David, an 18-year-old in Port Clinton, Ohio (Putnam’s home town), becomes a father. “It wasn’t planned,” David says. “It just kind of happened.” Putnam deftly weaves the stories into his analysis rather than just sticking them on top.

Our Kids provides a succinct, elegantly presented and state-of-the-art summary of social science in the areas of education, families, parenting and neighbourhoods. Here’s just one of Putnam’s depressing facts: affluent kids with low high-school test scores are as likely to get a college degree (30%) as high-scoring kids from poor families (29%).

Putnam is much less assured when it comes to solutions. In part, this is because he wants to persuade as many people across the political spectrum that there is a problem worth addressing. Most of his suggested policies are sensible, if unoriginal: home visiting, pre-kindergarten education, apprenticeships, closer school-community links, better community colleges. But they are insipid in light of the scale of the problem he has identified – a structural shift towards a class-based society. He is like a doctor diagnosing cancer and prescribing aspirin.

In part, the gap between problem and solution results from Putnam’s near silence on the economic dimensions of class stratification. He does point out that between 1983 and 2007 the richest tenth of parents increased spending on their children by 75%, compared with a drop of 22% at the bottom of the income scale. But he says almost nothing on the growing income inequality underlying such numbers. To be fair, there are shelves of new books on economic inequality and Putnam has a different set of interests. But the result is inevitably lopsided.

For the most part, the book has a tone of concern combined with cool, scholarly detachment. The one area where some real anger comes through is when Putnam describes the rise of “pay to play” after-school activities, caused by cash-strapped education districts imposing fees for clubs and sports. Waivers for poor kids are unused because of the stigma attached. “Close this book,” he urges, “visit your school superintendent and find out if your district has a pay-to-play policy.”

Our Kids is a better, sharper and more accessible book than Bowling Alone, which made Putnam’s name. Like his publisher, I hope the fame generated by the latter draws attention to the former. Our Kids will inform discussion and provoke debate. It is certain you will find something in the book to argue about. Putnam would be pleased about that, especially if the argument takes place during family dinner.

Our Kids is published by Simon & Schuster, £18.99. To buy for £15.19, click here