When comparing Nook vs Calibre, the Slant community recommends Calibre for most people. In the question“What are the best desktop readers?” Calibre is ranked 1st while Nook is ranked 9th.
Ranked in these QuestionsQuestion Ranking
Available for free from the Windows Store.
Pro Open Source
Calibre is available for Linux, OS X, and Windows, 32-bit or 64-bit.
Calibre has an optional portable build that can be stored on external media along with the users library. It can then be opened from the external media on any windows device.
Pro Powerful book management software, very customizable and scriptable
Features include metadata editing and downloading, coverpage downloading., book tagging and categorization, webpage-to-ebook converter for popular websites, etc. Lots of plugins available to extend functionality.
Con Windows 8 & 10 only
No Linux or OSX versions are available.
Con Average, non-power users might find the interface somewhat daunting
The interface, while functional is not the most attractive or intuitive which may put some people off and discourage their use.