Your tablet or eReader manual should list compatible file formats.
Overdrive, the company that powers the WVDELI, has a large list of devices, compatibile file formats, and links to manufacturer websites in the Device Resource Center. Scroll down on this page (or use control-F or the find command in your web browser) to locate your device and file formats.
For WVDELI instructions specific to your device (Android, iPad, Kindle, etc.), check out the "Get Started With" section here.
