title_body: Can I transfer my Purchased Nook library to Kindle or other Service?
upvoted_answer: Some authors and publishers require their books to be sold DRM free. Those books you can use on other reading platforms. Nook uses the ePub format which is used by just about everyone - Amazon being one of the exceptions. Depending on the specific reader, you might have to convert the file to a supported format. An ebook manager/converter program such as Calibre can help you with that.
  
  Beyond that, your options will depend on the type of DRM used. A web search for Nook DRM found a document from 2009 describing the Nook DRM as a proprietary form of encryption using a credit card number as the key. Assuming that is correct, then your options will vary depending on where you live. In the US, you do not have any legal options under current law, as the Digital Millennium Copyright Act (DMCA) prohibits the removal of DRM, except under certain special circumstances, such as visually impaired readers wishing to use text-to-speech.