DRM on old model kindles is trivial to crack, the key is apparently derived from your kindle's serial number. For this reason, I transferred all of my kindle

DRM on old model kindles is trivial to crack, the key is apparently derived from your kindle's serial number. For this reason, I transferred all of my kindle ebooks to my oldest kindle, and was then able to strip DRM from the entire library and convert to epub with Calibre+plugins. I wager there will probably come a day when Amazon refuses to send newly purchased ebooks to old models of kindles.