Any new technology eventually falls into line behind a standard. Writing seems to be following that path. Right now we have three main formats - Amazon's Kindle, Barnes & Noble's nook and following and gaining strength is ePub.
I have eight books listed on Amazon. Three are textbooks so they don't count. The rest are available either as paperback or kindle. Why Kindle? I write using Amazon's publishing tool "CreateSpace". I can simply move it to their kindle tool - KDP (Kindle Direct Publishing). I miss the fairly large Nook audience if I commit exclusively to Kindle - I would get a higher royalty. We are talking about .25 per book in a small - tiny - market.
Ok, to the point, I'm betting that at some point both Kindle and Nook will center on ePub. What do you all think?