When you sign a book contract with a publisher, you are not "selling" your book to them. You are licensing the rights for a specific term.
The book is always yours and you continue to own it. Once the publisher’s license is expired, your rights revert back to you.
In the section of your book contract labeled "Grant of Rights," you and your agent will negotiate what rights you license to the publisher, and what rights you hold on to for licensing by another party. For example, you may grant your publisher exclusive rights in the English language throughout the world to print, publish and sell the work as a soft cover (trade paperback) and to license a reprint edition by other publishers.
The "Grant of Rights" will then list additional rights that are yours to license such as book club rights, textbook rights, anthology rights. Other rights would include first serial rights (publication of condensations, excerpts, serializations in book from) second serial rights, large print rights, mass market rights, foreign language rights, audio rights, digital rights (eBook formats), motion picture rights, dramatic rights, TV, radio and allied rights as well as merchandising rights (lunch boxes and action figures).
So you see, "publication" is just the tip of what can become a very lucrative iceberg of rights. Subsidiary rights can earn both the agent and author additional profit, so it is important to pay attention to them.
This concludes your education as an author with the Rebecca Pratt Literary Group. You now are under the care of your agent who will help you through all of these processes and represent your work to the publishing industry, but you can always come back here to refresh your memory. Remember, however that these are general instructions and your agent may ask you to do things differently in your case. This course provides the basics but it is YOUR agent who markets your manuscript.