Hi, thanks for using JustAnswer.com I am Cris.
The nook are not repaired they are usually replaced if under warranty or a trade in fee to receive a another one. However if you have an older device you can purchase a new. You will not lose any books, any book you purchase remains in your B&N account. When you register a Nook with the account you instantly have access to re-download all of your books.
Also there is a Nook app which can be downloaded from a iPad, iPhone, Android phone or tablet. You can download the free app then log into your account and you will have immediate access to the books.
Let me know if you have any further questions. Please take the time to rate and submit my service..