To make sense of "free verse" in theory of in practice, the study of prosody—the function of rhythm in poetry—must be revised and rethought. In Free An Essay on Prosody, Charles Hartman develops a theory of prosody that includes the most characteristic form of twentieth-century poetry.
I chose this book because I had heard online that it was the best treatise to explain and defend free verse as a form of poetry.
My understanding going in was that free verse is poetry minus rhyme and meter. But I believed that there must be more to it than that. The point of Hartman's dissertation focuses not so much on the definition of free verse as a form of poetry, but in how free verse attempts to achieve rhythm (i.e. prosody) without using meter. I went in believing that language has a natural rhythm to it, and Hartman does seem to agree with that, and that effective free verse writers attempt to take advantage of that natural rhythm to improve the readability of the poem, and also to manage the reader's temporal (time) experience as they read.
This all seems like reasonable assertions, but unfortunately I found Hartman's defense of these ideas very difficult to follow. He does use a plethora of examples from the leading early proponents of free verse (Pound, Eliot, Williams, etc.) but Hartman is slightly less successful in his attempt to explain how these examples demonstrate his points in a clear and concise manner.
To be honest I found that reading through the chapters was like trudging through knee-deep mud. There were a few interesting ideas. I found his definitions in chapter 1 were the most helpful to me personally.
Maybe it is the best treatise on free verse, but for me it was disappointingly difficult to follow.
I gave up on this about halfway through. Dr Hartman tries to explain "why free verse works", but it seemed like the usual ad hoc justifications for poems which in my humble opinion work only somewhat if at all. Not that I can refute his "arguments" -- perhaps it's all just over my head. No stars.