I prefer to use PDF format, on letter size pages, arranged landscape.  thus far none of the other formats have the degree of control and range of features of PDF. Online it is easy to provide for a clickable table of contents, a professional index, and quality typesetting.

Where most PDF format e-books fall down is simple laziness. I don't take a paper book interior PDF file and slap it on the internet and call it an e-book. The online page has to have larger type than the paper book. and a format that fits the proportions of a computer screen.

for an example of what I consider the proper way to put together an e-book PDF please

download the following:

"Create Book Covers with Scribus"

http://www.booklocker.com/books/4055.html

The original cover I designed for this e-book is effective when printed out or viewed full size but really sucked when presented as a thumbnail.  The host company (Booklocker.com)  just wouldn't accept it. So I designed and uploaded a completely different cover image for the online presentation.  Actually I want through several revisions

before I came up with one that they liked and I liked.  You get that kind of personal attention from a smaller outfit like Booklocker. Here is the final image:

Now it may be that you disagree with my approach. Well, that is why you can reply to this post--see below.

In any case let me hear your thoughts.  Feedback, positive or negative, is always welcome!

John Culleton