Calibre is an open-source program for managing your e-book collection. It provides a simple interface with large buttons for adding, editing, converting, and viewing books. You can browse your book collection using covers, titles, tags, authors, publishers, etc. Calibre can automatically download all the metadata for an e-book such as title, author, publisher, ISBN, tags, cover, and summary.
Calibre has a built-in e-book viewer that can display all the major e-book formats. It has full support for Table of Contents, bookmarks, CSS, a reference mode, printing, searching, copying, multi-page view, and embedded fonts.