Oh... and one of the reasons for using Calibre is that there is an (unofficial) plugin by Apprentice Alf/Harper/others that can remove DRM* from e-books when importing them. This is absolutely essential for me, because I buy books long before I ever get around to reading them (because of pricing, and interest in them, sometimes having Calibre pick a random book), because I want to fix them if necessary, and convert them to the format of one reader or another. My entire library is in EPUB (cleaned, fixed and tagged), but I've used it on both a Kindle in AZW3 format and now on Kobo in a KEPUB format.
If DRM-removal hadn't been possible, I wouldn't even have considered getting into ebooks. I possibly wouldn't even read as much as I do now.