What if your publishing agreement doesn’t expressly have a reversion clause, or did not include a license allowing you to do something you want with your work? You should try negotiating for rights reversion or a license with your publisher anyway. Negotiating for a rights reversion is particularly useful where a book that you have written is out-of-print. The publisher might be willing to assign rights back to you, if they have no future commercial plans for the work, or allow you to publish an E-Book version while retaining rights to the print medium.
A good resource for learning more about how to negotiate a rights reversion, even if the publishing agreement you signed didn’t contain one, is Authors Alliance’s guide Understanding Rights Reversion (pp. 70-100).
If your publisher says No! or just never responds you might not be out of luck. There is a right that arises automatically under the copyright statutes. This is called Termination of Transfer.
For works created after 1978, Section 203 of the Copyright Act allows for the termination of transfer after a certain period of time has lapsed. But the conditions to exercise the right are strict--and exercising those rights can be complicated. To help you get started, the Authors Alliance and Creative Commons have tried to make it easier for authors to determine whether they qualify for termination of transfer rights by creating the Termination of Transfer Tool. As they explain about the tool:
This tool is designed to raise awareness of the termination of transfer provisions, to encourage authors to figure out whether the termination rights of U.S. copyright law may be relevant to their works, and to help people understand how termination of transfer works.
Creative Commons has a video explaining how the termination of transfer tool works featuring an actual academic authors demonstrating how to use it for one of her works published in the 1970s.
The 30,000-foot view of termination of transfers:
A 5-year window opens 35 years after you have transferred your copyrights (with some important exceptions)
During that 5-year window, you can obtain a termination of transfer.
Notice of termination must be giving at least 2 years but not more than 10 in advance of the termination date
Notice must be serviced on the Grantee (entity your transferred copyrights too) and/or any successor-in-title (entity that subsequently got the copyrights)
Because the statutory operation of the termination of transfer is complicated you will most likely need to consult an attorney specializing in Copyright Revision