I posted this on another thread, but in answer to someone's question about popular formats, smashwords did a survey:
http://blog.smashwords.com/2009/03/w...ks-matter.html
Edward Patterson published this helpful guide on publishing ebooks (his experiences and recommendations and he has a lot to say) It happens to be a free download, making it even more useful:
https://www.smashwords.com/books/view/316
Me, I'm still learning. I can say that the biggest problem is finding a place where enough readers go. Amazon works very well for that precise reason. Tons of readers go there. For any other format, it's a battle to find the readers because there are simply too many sites--it's impossible to go to all of them to get one or two or 10 readers.
It's also a changing scene with new devices coming out and new converts to e-books joining daily!
Maria
Sage: (multiple formats; Amazon or Smashwords--$1.00)
Catch an Honest Thief (Kindle only format: $1.99; a cozy mystery)