Check out this handy cheat sheet from the Overdrive Digital Libraries blog:
eBook Devices Cheat Sheet: A librarian reference tool
The blog post answers the question as to why Adobe Epub and PDF formats cannot be used on a Kindle. Useful.
Things can change quickly and there are sometimes work-arounds but this is a useful summary of the state of the ebook device world for libraries at this date.
Stephen
JUST what I needed! Thanks!