Lauded poet Christopher Merrill hatched a brilliant plan: invite six other poets to join him in four days of writing in Iowa City. The poets would write for 30 minutes, creating a poem of 15 lines, and then read it aloud to the group. As poets heard the poems, they noted memorable words, images, and lines, which they would borrow to insert in subsequent poems of their own. These rounds continued, until, in a process of call and response and unprecedented...