"simple command-line utility for extracting text from EPUB documents and, optionally, re-flowing it to fit a text display of a particular number of columns. It is written entirely in ANSI-standard C"
"tool to convert PDF articles (newspaper, academic) to MOBI or EPUB documents"
Convert files from one markup format into another. Pandoc can convert documents in markdown, reStructuredText, textile, HTML, or LaTeX