If you're giving the book away, why not release the source (LaTeX, Word, whatever) in addition to your favorite subset of {PDF,EPUB,...}? Then readers who want a different format have a better chance of being able to produce it themselves.
If used well EPUB is suitable as the source (more than Word anyway). It's generally just HTML with some metadata.
I think it is (in theory) even allowed to make an EPUB of LaTeX files, except that EPUB readers aren't required to support LaTeX (you're also allowed to provide both HTML and LaTeX, although the W3C probably expected people to use that part of the standard for audio-books).
Outside of dedicated enthusiasts, I don't think the average reader wants to take the time to "compile" their book.
Most commercial services these days (if my HumbleBundle books from O'Reily are any indication) simply provide pre-compiled editions in EPUB/MOBI/PDF format, as this seems to cover 95% of use cases.
