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.

• Cover Grid: Dynamically adjust the size of the in memory cover thumbnail cache based on the window size to ensure flicker free rendering even on very large screens.
• Template tester: Remember last used template
• Get Books: When downloading books show a popup message telling the user that the books will be added to the calibre library automatically, to help new users understand what is happening. The popup message can be disabled.
• E-book viewer: Try to detect when a chapter has a page break before the start of the chapter's text resulting in a leading blank page and override the page break.

• Edit metadata dialog: Fix the author sort field not being marked red initially when the author sort does not match the author due to a Qt 5 behavior change.
• OS X: Fix restarting of calibre not working if calibre.app is placed in a location with spaces in the path
• Fix regression that caused calibre running in debug mode on OS X to not have a menubar or dock icon
• Get Books: Fix downloading ebooks from Project Gutenberg via the builtin browser not working because of changes to the Project Gutenberg website.
• Get Books: Update Gutenberg plugin for changes to the Project Gutenberg website.