Robert Lowell, Elizabeth Bishop, Sylvia Plath, John Berryman, Randall Jarrell, and Delmore Schwartz formed one of the great constellations of talent in American literature. In the decades after World War II, they changed American poetry forever by putting themselves at risk in their poems in a new and provocative way. Their daring work helped to inspire the popular style of poetry now known as "confessional." But partly as a result of their openness,...