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.
osis2epub is a a program that converts a Bible text stored in Open Scripture Information Standard (OSIS) format to an EPUB book. The resulting eBook can then be read on various eReaders or converted to another format. Conversion to a simple text format and to a collection of HTML files with an accompanying stylesheet and file list (for direct viewing or subsequent conversion) is also supported.