Acclaimed Russian-American journalist Masha Gessen is uniquely able to tell us. A teenage immigrant herself, she returned to Russia to cover firsthand the transformations that wracked the region from the 1990s on. It is there that she begins her astonishing account of the Tsarnaev brothers, descendants of ethnic Chechens deported to Central Asia in the Stalin era. Following the family in their futile attempts to make a life for themselves in one war-torn locale after another and then, as new emigres, in an utterly disorienting new world, she reconstructs the brothers' struggle between assimilation and alienation, which incubated a deadly sense of mission. And she traces how such a split in identity can fuel the metamorphosis into a new breed of homegrown terrorist, with feet on American soil but sense of self elsewhere.