It's been several years now since the numbers of online book sales in a month out - did the traditional bookstores. (jwikert.typepad.com)
For most self - published authors, it makes more sense to focus on online book sales where there is still some profit to be made and far fewer headaches. (nonfictionauthorsassociation.com)
One source of numbers for online book sales, including for indie ebooks, is the website Author Earnings. (feedspot.com)