It speaks volumes that almost a century and a half after Baudelaire’s Paris Spleen announced the modern prose poem, James Longenbach influentially defined poetry as ‘the sound of language organized in lines’. An otherness, bordering on illegitimacy, pervades what Cassandra Atherton and Paul Hetherington argue is ‘the most important new poetic form to emerge in English-language poetry since the advent of free verse’. The book vindicates this claim. No less compelling, however, is the way the prose poem, long defined in negative terms, here becomes the whetstone over which old assumptions – about the prosaic, the poetic, and the daylight between the two – are run to a fresh sharpness.