In 1798, William Wordsworth and Samuel Taylor Coleridge were engaged in a top secret experiment. This was not, as many assume, the creation of a book of poetry. A book emerged, to be sure—the landmark Lyrical Ballads. But in Murder Ballads, David John Brennan posits that the two poets were in fact pursuing far different ends: to birth from their poems a singular, idealized Poet. Despite their…