Contracts are a major part of the traditional publishing model, but they shouldn't be a part of self-publishing. Why would a contract be necessary? YOU are the writer, the publisher, the copyright holder … there is no third party to deal with, other than your book printer. If the printing or self-publishing company you are talking to is trying to get you to sign a contract or "agreement," we'd strongly advise you to proceed with caution. If you do choose to work with a company that makes its self-publishers sign book publishing contract terms, you should definitely have a lawyer look it over before you sign it. If you sign the wrong contract, you might end up losing the rights and royalties to a potential audio book, the ebook, or even future edition updates. Be very careful! It's very important that you make sure you retain the rights to your work. That's one of the main reasons you chose the self-publishing path, right? To exclusively maintain the rights over your work!