Amazon Kindle Store offers ebooks in AZW, MOB and PRC formats. You can read them on your
Kindle readers or using free
Kindle apps. If you get another Kindle or Kindle app, you should be able to get your ebooks from
Amazon again.
But if you want to backup your
Kindle Store ebooks on your computer, you need to remove DRM protection from them. Then you will be able not only to backup, but also to convert your ebooks to read on other devices including
Sony Reader,
Nook,
iPad,...
You don't need to be a hacker to crack the encryption of DRM protected Kindle files. Just download a freeware Kindle DRM removal plug-in for freeware
Calibre.
Download freeware Kindle DRM removal plug-in for Calibre and freeware standalone Kindle DRM removal tools:
ebook DRM removal tools archive