FictionBook is an XML-based e-book format. The purpose of the FictionBook format is to provide a way to store books in a structured way, preserving the book's formatting and metadata. It is designed to be easily converted to other formats, such as PDF, EPUB, or plain text, and is well-suited for archiving and long-term storage of electronic books. The format supports various elements like titles, authors, paragraphs, poems, epigraphs, and notes. It also supports basic formatting like bold, italics, and superscript. Metadata such as author, title, ISBN, and publication information are also stored within the file. FictionBook files are typically small in size and can be easily shared and read on a variety of devices and software. The format is open and royalty-free, making it a popular choice for independent authors and publishers.