Epublib is a Java library for managing epub files. It is capable of reading and writing epub files programmatically and from the command-line tool. Epublib consists of two parts: the core and tools. The core runs both on Android and a standard JVM. Tools require a standard Java environment. Other features include a builtin Swing-based viewer and comprehensive coverage of the epub standard, supporting the spine, the table of contents, and the guide. The API is designed to be as simple as possible, while at the same time making complex things possible too.
eBook parser library is a Java library designed to handle the epub and fb2 e-book file formats. It retrieves information such as title, author, genre, series title, etc, and can be used to process or organize databases of large numbers of e-books, where speed is essential. To maintain speed, it does not extract all content from the e-book or check the structure for errors.
mdepub is a tool that allows you to compose a book in Markdown format and use Pandoc and Calibre to compile an Epub package including all of the book's source material. In effect, you can keep the source and product in the same file in your library; if you ever want to revise the product, you merely need to extract the source, make edits, and recompile.