http://www.digitalbookworld.com/2013/bi ... ook-stats/
Here are the retail sales numbers:
Amazon came in at 67.0%, B&N Nook 11.8% and Apple iBooks at 8.2%. The “Other”section had 12.8%. Although “Other” was not broken out, it probably consists of Kobo, Google, Sony for retail; direct from publishers or perhaps the public library.
And this about what books do or do not do well in digital:
The results are in-line with traditional thinking in that the top ebook categories are Romance/Erotica; Thriller/Mystery; General Fiction; Religious Fiction and YA Fiction. Quick reads and stories have continued to do well in digital.
Of the 14 categories listed. 10 have a stronger preference for digital.
The four categories that have the strongest physical book preference are Cookbooks; Graphic Novels; Travel and How-To Guides. These categories are all still strong on-line but not via traditional ebooks. Many digital content sales are in Cooking (allrecipes.com); Graphic Novels (comixology); Travel (fodors.com) and How-To (YouTube) but not ebooks. All are also options for Apps which is not included in ebook numbers and can be a substitute.
Those who've not yet got into digital might want to look into what Smashwords offers. Send them a properly formatted Word or ePub file and you'll reach every major retailer but Amazon.