Calibre is a free and open-source ebook management tool that enables users to organize, convert, and view their ebook collections in one place. It allows users to easily categorize their ebooks by author, title, series, and add tags for better searchability. Calibre also enables users to edit ebook metadata, including author name, title, and cover image. Additionally, it can convert ebooks from one format to another, making them compatible with different devices. The built-in ebook reader allows users to read their ebooks directly within the software, and it includes features like bookmarking, highlighting, and font customization. Calibre is a user-friendly and comprehensive tool that provides a seamless experience for managing and enjoying ebooks.