Ever since Donald Trump was inaugurated as president, bookstores have been flooded with volumes attempting to explain America’s unraveling.

George Packer’s Last Best Hope, published earlier this year, provided one of the best diagnoses. But this new volume by New Yorker staff writer Evan Osnos offers the most personal and the most powerful description yet of a country “so far out of balance that it [has] lost its center of gravity”.

To tell a story bookended by the attacks of 9/11 and the assault on the US Capitol on 6 January this year, Osnos travels to three places in which he has lived: Greenwich, Connecticut; Chicago; Clarksburg, West Virginia. His subjects range from the decline of local newspapers and the opioid crisis to the tremendous hidden costs of idiotic wars in Iraq and Afghanistan.

But the leitmotif of the book is best captured by a phrase he cites from the great liberal economist John Kenneth Galbraith, who described “one of man’s oldest, best financed, most applauded, and, on the whole, least successful” quests: “The search for a truly superior moral justification for selfishness.”

Osnos’ book is replete with ghastly statistics. The three men – Bill Gates, Warren Buffett and Jeff Bezos – who have “more wealth than the entire bottom half of the US population combined”. The CEO salaries which spiraled from 20 times as much as a frontline worker in 1965 to 278 times in 2019. The fewer than 200 companies with Washington lobbyists in 1971 to the 2,500 that had them just 11 years later.

But what makes the book come alive are the personal stories. Billionaires, coal miners and soldiers who suffer from post-traumatic stress, and all the evidence Osnos offers of failure to control excess at the top or provide meaningful help at the bottom.

Above all this is a story of how mega-rich Americans have invested hundreds of millions of dollars to give themselves the power to pillage the earth, destroy the air and corrupt democracy in a thousand ways without ever being held to account.

Lee Hanley is a perfect example. A Yale graduate and Greenwich resident, in 1980 he dumped George HW Bush for Ronald Reagan. Osnos’ keen eye provides a crucial detail about how Hanley’s wife, Allie, pinpointed Regan’s greatest flaw before presenting him to the Connecticut gentry: “He had on a brown tie and it was ghastly. When you go to a different part of the country, the most important thing you need to do is dress like they do. So I ran to Bloomingdale’s and bought four ties.”

Reagan “wore them in all the posters after that”.

Hanley spent millions more than his wife. In alliance with Richard Scaife, Robert Mercer and the Koch brothers, he trained “a generation of Republicans to adhere to ideological orthodoxy” with “a string of historic political investments”.

“He saved the conservative publisher Regnery with an infusion of cash, he founded a Connecticut affiliate of a network of think tanks to advocate for low taxes and small government, and he became the principal backer of a political consulting firm formed by Roger Stone, Charlie Black and Paul Manafort, whose early clients included Rupert Murdoch and Donald Trump.”

Rarely has a handful of clever investments done more damage to more people.

In West Virginia, where Osnos once worked for the Exponent Telegram of Clarksburg, he offers a nuanced history of a state’s transformation from hardcore Democratic to reliably Republican. A West Virginia think tank funded partly by the Kochs made a moving argument against mine-safety regulations – “Improved safety conditions result in lower money wages for workers” – then asked, “Are workers really better off being safer but making less income?”

Then-governor Joe Manchin asked the author of the study to brief his cabinet and a joint session of the state legislature finance committees.

Juxtaposed with the lobbyists’ many successes are heartbreaking tales of ecological catastrophe spawned by coal companies removing mountain tops. Osnos also reminds us of Manchin’s first big contribution to the national political discussion, when he ran for Senate in 2010: an ad in which he fired bullets through climate-change legislation.

“For decades candidates had been photographed with guns,” Osnos writes, “but this was the first time anyone had assassinated a piece of proposed legislation on film.”

Four years later, an Arizona Republican “upped the stakes” by shooting the Affordable Care Act with “a handgun, a rifle and a semiautomatic”.

There is so much more in this book, including the horrific fact that America has now accumulated 310m private firearms, the highest rate of civilian gun ownership in the world.

“The second highest,” Osnos writes, “was Yemen, which had barely half the rate.”

The story of the electoral backlashes, when Democrats took the House in 2018 and the White House and Senate in 2020, is one of Osnos’ only hopeful sections. The right has spent so much money to end government regulation and purchase elections, especially since the disastrous supreme court decision of Citizens United, it is astonishing American democracy has survived at all.

America’s richest “launched a set of financial philanthropic and political projects that changed American ideas about government, taxes and the legitimacy of the liberal state,” Osnos writes.

“In every element of his commercial and political persona, Trump was a consummation of that project … Most of all, of course, he stood for a belief in unbridled self-enrichment, and on that basis some of his most genteel supporters were willing to overlook” every other disgusting thing about him.

Osnos says the assault on the Capitol reminded him of an observation by Lincoln’s secretary of state, William Seward: “There was always just enough virtue in this republic to save it; sometimes none to spare.”

My hope is that everyone who reads this great book will be enraged enough to redouble their efforts to undo the damage the greedy have wrought, and to take back America for its decent citizens, once and for all.

• Wildland is published by Farrar, Straus and Giroux