Definitely "Lonesome Traveler", but I recently read another book about Hays (with a lot of his published and unpublished writings) called "Sing Out Warning, Sing Out Love" that I would highly recommend.

As far as the books on Woody Guthrie by Joe Klein, Ed Cray and Jim Longhi respectively, I would say they should all be read; each book has gaps and/or flaws that require reading the others to fill in the story and get a more rounded picture. At least, that's my opinion. There's also a book on Guthrie by Elizabeth Partridge that, though aimed at slightly younger readers, is worth looking at.

I also found "The Life and Legend of Leadbelly" by Charles Wolfe and Kip Lornell well worth my time.

Ditto Dave Van Ronk's autobiography.

I have to admit, though, that when I saw the title of this thread I immediately thought of a "biography" that wasn't a book: the film "Alice's Restaurant."