Calibre is a free and open-source e-book management software that allows users to manage their e-books, convert between different e-book formats, and sync e-books with various devices. It was first released in 2006 and has since become one of the most popular e-book management tools available.

One of the most notable features of Calibre is its ability to organize e-books into different categories and add tags, making it easy to search and locate specific books. It also allows users to edit the metadata of their e-books, including the title, author, and cover image, and can even download missing metadata from online sources.

Calibre also provides a powerful e-book conversion tool, allowing users to convert e-books from one format to another, such as from EPUB to MOBI, or from PDF to EPUB. This is particularly useful for those who want to read e-books on different devices that may not support the same file format.

In addition, Calibre supports a wide range of e-book readers, including Amazon Kindle, Barnes & Noble Nook, and Kobo e-readers, and can automatically sync e-books with these devices. It can also connect to online e-book stores, such as Amazon and Google Books, allowing users to browse and purchase e-books directly from within the software.

Calibre is an essential tool for anyone who reads and manages e-books. Its powerful features and easy-to-use interface make it a must-have for anyone looking to organize, convert, and sync their e-book library.

Key Features:

• Library management system to organize e-book collection
• Format conversion for compatibility with different devices
• Built-in editor to modify e-book metadata and table of contents
• E-book viewer with customization options
• Integrated web browser for downloading e-books
• Synchronization options for keeping e-book collection up-to-date across devices
• Extensible with plugins to add additional features and functionality.

• E-book viewer: Add support for touchscreens when running on Windows tablets.
• Sending by email: Add an option to insert the comments from the book metadata as text into the email. Useful to allow the recipient to see a summary of the book before opening it. The option is in Preferences->Sharing by email
• Edit book: new tool to automatically generate an inline (HTML) Table of Contents based on the current NCX Table of Contents. Accessed via Tools->Table of Contents->Insert inline Table of Contents.
• Edit Book: Add a check for internal links in the book that do not point to HTML documents
• Kobo driver: Add support for the soon to be released firmware version 3.2
• Completion popups: Allow pressing Tab (in addition to Enter) to accept the current completion
• Edit book: When auto-fixing named entities, fix in all files not just current file.

• EPUB Output: Do not override any declared text-decoration CSS for tags when auto-converting them to (auto-conversion is needed to comply with the epub spec).
• Windows: Improve handling of non-ascii characters when the command line utilities are outputting to the windows console
• PDF Output: Fix incorrect rendering of html files with only a single large image and very little text. In some rare circumstances, the full html file would not be rendered.
• Add a copy to clipboard button for the duplicates message when copying to another library.
• Catalogs: Fix an error when generating catalogs via calibredb from the command line on non-English installs
• Catalogs: Fix an error creating catalogs in ebook format when one of the books contains HTML entities in its title
• Preferences: When using the Restore to defaults button for the Tweaks, remove all plugin tweaks as well. This allows the user to recover the tweaks file if one of the plugins insert invalid code into the plugin tweaks
• Edit book: Fix previously used locations for file open dialogs not being remembered when edit book is launched from within the main calibre program
• Edit book: Fix a couple of temporary files occasionally not being cleaned up on program exit in windows