Music: Kevin MacLeod Instructions on how to extend your textbook rental at BookRenter.com: 1) Log into your account 2) On the left side click "extensions and buy outs" 3) Select the book rental you want to extend, and pick the extension period you want 4) Proceed through the check-out process to purchase your rental extension 5) Confirm your shipping address and payment Continue Reading about How to extend a BookRenter.com textbook rental