What are some alternatives?
When comparing Amazon Kindle and calibre, you can also consider the following products
FBReader - FBReader is an e-book reader for various platforms. Features:
Cool Reader - Fast and small cross-platform eBook reader for desktops and handheld devices
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
The new iPad Pro - 10.5 inch - Thinner and better
Adobe Digital Editions - ebook reader software
Kobo Books - Kobo Books is a best in the class eBooks and eReadering apps for many reasons.