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.

• Prevent calibre from installing or running on Windows XP as there have been many reports of Qt 5 crashing on Windows XP and Windows XP is now no longer supported by Microsoft. If you are on Windows XP, please stay with calibre 1.48 until you are ready to upgrade your windows.
• Kobo driver: Add support for new Kobo Aura H2O and firmware 3.8.0
• Driver for HTC C.
• Add a new tool to easily test templates. Go to Preferences->Toolbars to add the tool to one of the calibre toolbars.
• EPUB and MOBI catalog generation: Allow using the full template language including all custom columns

• E-book viewer: Fix soft-hyphens causing rendering artifacts with some fonts due to a bug in Qt 5
• OS X: Workaround for Qt 5 bug that causes the popup menu on the author to author sort button in the edit metadata dialog to not respond if the mouse button if not released once before clicking menu entries.
• Book list: Fix Ctrl+Home/End not selecting the first/last book
• PDF Output: Fix header and footer templates not working in calibre 2.0
• OS X: Workaround for Qt 5 bug that caused many keyboard shortcuts to not work in OS X
• Workaround for Qt 5 regression causing custom colors in color chooser dialogs to not be remembered between calibre sessions
• Conversion: Fix error when converting EPUB/HTML files that contain invalid margin or padding declarations.
• Fix for calibre 2.0 crashing on startup on some linux systems when used with --detach
• E-book viewer: When right clicking on an image to view it in its own popup window, fix the rotate button not working correctly with the zoom buttons
• Workaround for Qt 5 bug causing crash when running jobs (conversion to PDF or MOBI; reading metadata from an EPUB without a cover) that require Qt WebKit on Ubuntu.
• OS X: Fix background jobs stealing input focus if they require the use of Qt WebKit
• Preferences->Metadata plugboards: Show plugboards for disabled devices and formats whose metadata writer plugins have been disabled.
• Fix calibre 2.0 not using system color scheme on windows and OS X
• Fix regression in calibre 2.0 that caused crashes when using drag and drop to re-order virtual library tabs
• Linux: Disable the optional system tray icon because of bugs in the system tray icon implementation in Qt 5 on linux.
• E-book viewer: Fix navigating to a bookmark not updating the displayed page number.
• Fix the 'unified title and toolbar on OS X' tweak causing calibre to fail to work because of a bug in PyQt5
• E-book viewer: Fix a regression in 2.0 that changed the speed of scrolling with the mouse wheel in flow mode
• Edit book: Workaround for regression in Qt 5 that causes typing the Cmd+some letter to generate text in the editor instead of being ignored.
• Book polishing: Fix EPUB files with corrupted ZIP central directories not working and leaving behind detritus in the current working directory.
• Edit Book: Workaround for Qt 5 regression that caused the 'See what changed' tool to freeze the editor when closing the window showing the changes.
• Fix regression in 2.0 that broke viewing of LRF format ebooks.
• Fix for a Qt 5 regression that caused the Copy to Library right click menu to be empty on OS X.