Over at Brainstorm, John L. Jackson Jr. has some good advice about how to turn your dissertation into a book. He offers two main pieces of advice:
1). Don’t write a dissertation, write a book. In other words, when you write your dissertation think about potential readers and imagine the dissertation as your first book. This is good advice if you want your first book to be an academic monograph published by a university press. But if you do not want your first book to be an academic monograph that will be read only by those in your sub-discipline, you may want to just get the dissertation finished, land a job, and then write the book you want to write.
I recently gave this advice to a graduate student who wanted his first book to be a narrative history, but did not feel he could get away with writing narrative in his dissertation. I advised him to earn his scholarly credentials by finishing the dissertation and then write a narrative history as his first book.
2). Offer your book manuscript to multiple publishers at once. This was once frowned upon (and still is for academic journal articles), but it is becoming increasingly more common. This makes sense to me, especially as university presses seem to be taking longer and longer to complete the review process.
In the end, I do not think that there is any one formula for turning a dissertation into a book. Some young scholars rip the title page off the dissertation, tweak a few transition sentences, scale back a few long footnotes, and land a book contract. Others, like me, write dissertations that do not translate well into book form. Their projects need substantial revisions before they are published.