The Tsarnaev Brothers: the Road to a Modern Tragedy by Masha Gessen, book review

Boston bomber brothers' story features no elaborate conspiracy – just resentment

Mass destruction: the aftermath of the Boston bombing on 15 April 2013 (AP)

Shortly after lunch on 15 April, 2013, Patriots Day in Massachusetts, a bomb went off at the Boston marathon, killing three bystanders and blowing the limbs off another 16. This May, a US Federal court sentenced Dzhokhar Tsarnaev, one of two brothers, to death for the crime. He showed no emotion at the verdict. His brother, Tamerlan, was dead already, killed in a shootout with police soon after the explosion.

What drove tousled-haired Dzhokhar and Tamerlan, a young man with matinée-idol good looks, to want to murder a lot of joggers? Americans have agonised over their motives, wondering whether they were "radicalised" in the US or drawn into the Islamist underground by contacts back home in the Caucasus.

Gessen's exhaustively researched account, which tacks back and forth between America and the ex-Soviet "stans", will disappoint those who imagine that if only "X" had been done, "Y" would not have happened.

No doubt it would comfort some to learn that the Tsarnaev family had been victims of some appalling injustice in America or back "home", and that crushed ideals somehow turned a couple of innocents into terrorists. But the Tsarnaev family do not appear to have had many ideals – just a hazy notion that the streets of America would be paved with gold. They did not lack for help in America. Finding a decent place to live can be hellishly difficult for immigrants to the US but the Tsarnaevs landed on their feet in Boston. A well-meaning liberal landlady in nearby Cambridge offered them a place in her home. The boys went to Boston Latin. That's no sink school. Founded in 1635, its graduates include several former presidents of Harvard as well as President Kennedy's father, Joe.

The liberal landlady, various teachers and other well-wishers seem to have done their best to open doors for the Tsarnaevs. But nothing worked out for this diffident, touchy, needy family. The parents chopped and changed jobs. The father's temper antagonised the neighbours. One of the daughters was done for shoplifting. Tamerlan had a budding career as a boxer but drifted off into selling pot.

Around 2009, Mrs Tsarnaev seems to have given up on America. Back home in the stans, neighbours had nicknamed the elegant couple "the swans". But now this particular swan felt her wings had been clipped. She chucked out her smart skirts, put on a headscarf, decided the Jews were to blame for everything and absorbed herself on the internet in the Protocols of the Elders of Zion, whose theories she shared with her sons. They fell behind with the rent. Even the liberal New England landlady baulked at hearing her tenants spouting anti-Semitic codswallop and told the family to move on.

The parents drifted back to Dagestan in the Caucasus, equally furious with America but now separated from one another. The boys stayed on, Tamerlan drifting around the University of Massachusetts, smoking pot and sleeping late. His roommate remembered little about him except that his bed was a mess. In 2012, he went to Dagestan where he told friends that he was now devout and considered America morally degenerate. The serious Muslims of Dagestan agreed but found him theologically illiterate, which was not surprising. Like his mother, he seems to have picked up most of his ideas about Islam, Jews and American degeneracy on the internet.

A Russian-speaking immigrant to America herself, Gessen has a fine understanding of the complex mores and neuroses of the small community of immigrants from the ex-Soviet Caucasus in Boston, a society bound by numerous prohibitions and an all-consuming fear of loss of identity.

In the case of the Tsarnaevs, credulous faith in their golden prospects in the land of the free curdled first into resentment and then into a murderous hatred. That's more or less it. No elaborate conspiracy, no predatory imams, just an American dream that went very, very sour. Gessen says that obsessing about who "radicalised" the Tsarnaev brothers is pointless, a trail that leads nowhere. The people in this story, she concludes, were few, their ideas uncomplicated and their plans all too achievable. And that, she warns, "is the hardest and most frightening story to believe".