When a publisher buys the rights to a book it intends to publish, the author grants the publishing company the right to do so under the copyright law. The author must also agree not produce or try to publish any other works that may "compete" with the work the author just sold to a publisher, that the work is the author's (author's warranty), and that the manuscript will be prepared and delivered as agreed upon between the publisher and author.
Publishers also have the right to change the manuscript and must incur the cost of copy editing, proofreading and editing. The publisher may try to charge the author for these corrections and changes to be made to their manuscript, though the author should not have to pay for these if it is due to the publisher's oversight. A set number of rewrites and polishes should be agreed upon between the author and publisher before the publisher turns the book over the to the copy editors and proofreaders in the final stages of production, before the book is sent to the press.
Authors should receive royalties off the sales of their books and this should be agreed upon when they sell the rights. The most money a first-time to moderately successful author can realistically expect to receive in royalties is fifteen percent per copy of the book sold. Though all contracts are different, royalties are also usually staggered based on book sales. A lower percentage of royalties are given for the first 5,000 copies that are sold, and a larger percentage is given with the next 5,000 copies that are sold. The maximum percentage of royalties will be paid with all subsequent copies of the book that are sold.
Small advances of money are given by a publisher in order to support the author while he writes the manuscript. Larger advances are sometimes given by publishers to lock down rights of a book from a very popular author. These advances can be in the six to seven figure range. Nevertheless, for most authors, advances are pretty low, averaging in the mid four figure to low five figure range.
When copies of a book do not sell, a publisher may declare the book out of print. The International Standard Book Number (ISBN), will be updated to reflect the book's status. There may be a set procedure the author has to go through to get the rights of the book back from the publisher. However, the writer can usually have these rights reverted. If and when the rights are reverted to the author, the book will be available for publication. The author may chose to self-published the book, or attempt to have the book republished by a different publisher.