http://www.amazon.com/Broken-Thing-Poets-Line/dp/1609380541/ref=sr_1_1?s=books&ie=UTF8&qid=1321986713&sr=1-1
Why does the poet stop the line (line break) when he or she does? It is not a simple decision since the 20th century arrived and poets began to experiment with more than traditional blank verse that consisted of repeated predictable patterns of stressed and unstressed syllables.
Where does a line end or begin in a poem? Its intent, content and form is not the same as a line in prose. Reading A BROKEN THING- POETS ON THE LINE is like falling into an alternate universe where words, sounds, pacing, silence, page margins, enjambment, compression, wide open spaces all take on a powerful vibrant life of their own. Political views can even be seen in the construction of the line! A poem is not a static thing. The variation of structure are endless.
Think about this-
When a line ends there is often silence. What does that silence do? Is the empty space in a line soundless?
In this book of essays poets tell readers how they see the line and how they use it in their work and how others use it.
I particularly enjoyed these essays:
Who is Flying this Plane?
The prose poem and the life of the line by Hadara Bar-Nadua.
Croon: A Brief on the Line by Tim Seibles
Three Takes on the Line by Catherine Barnett
This is an anthology you can read again and again.
Read more about blank verse (the traditional poetic form) here
http://www.uni.edu/~gotera/CraftOfPoetry/blankverse.html