FYI - You only need to "return" an e-book if you want to return it early. If you keep it for your entire checkout period, the e-book will return itself.
Kindle e-books from OverDrive have a checkout period just like printed materials in libraries do. The big difference, however, is that you do not have to return the e-books - they just disappear from your e-reader. How do they do this? Using a technology called Digital Rights Management (DRM).
But what if you'd like to return a Kindle e-book early? The e-book must be deleted from your Amazon account. The next time your Kindle connects to wireless, it will be deleted from your device.