The top formats for ebooks these days (in no particular order) are ...
Of the above mentioned formats, PDF is the worst one. Not very friendly at all. BBeB is for the Sony Reader, eReader is for small screen devices such as a PDA. If you read eReader books on your computer,m you'll want to stop reading. MobiPocket is available on the iLiad and hopefully soon n the Cybook Gen3. MS Reader is the best of the ebook formats for reasons that have been mentioned all over the forum.