It would depend on the contract, some contracts buy the rights to a book, which means (again depending on the wording) that they own it, they can make changes to it and your book may turn out very different from what you intended. It also means they can sell it.
Authors need expert legal advice.
Research is an important part of writing, and researching publishing contracts and all that go with them is even more so. http://www.fonerbooks.com/contract.htm