Agent Rachel Gardner of WordServe Literary Group has an excellent blog post of getting the rights back from publishers for the books that are no longer available. You can read the full post here, but here is an excerpt:
"Reversion of rights" simply refers to the point in time at which the publisher no longer owns the rights to your book. When the rights revert to you, the author, you're free to
Published on December 08, 2010 04:00