Thought I will keep some directions on desktop publishing. The most widely used format is PDF (portable document format). It is versatile and maintains a structured and consistent layout to the contents.
The other format that is now open is EPUB format. Currently its on 3.0 and now a widely supported open format for digital books using xml. If you are a publisher, so is interested in self publishing, the following opensource tools might help:
- https://code.google.com/p/sigil/
- http://www.sourcefabric.org/en/booktype/
- http://calibre-ebook.com/