Good question, good site, wrong part of the site.
You need to use the "Find a Lawyer" function at the top or at the bottom of this page.
Active Avvo participant Pamela Koslyn has a very good reputation in this field among her Avvo colleagues.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Do you have a not-for-profit organization in your area that assists authors in situations like yours? In my state we have an organization that helps authors with issues like yours: the Writers League of Texas. if your state has a similar organization, then that organization would probably be able to provide some wonderful resources!
Answers to questions are for general purposes only and do not establish an attorney-client relationship.
All of the recommendations here are good. Since the "process" you are referring to can be a long one, feel free to consult with a few attorneys to make sure they understand your goals and that you feel comfortable working with them long term. Best of luck with your book!