Amazon makes up a higher percentage of the total US ebook market than the oft-cited 65% figure: when indie books without ISBNs are included in the statistics, Amazon accounts for 74% of all US ebook purchases and 71% of all US consumer dollars spent on ebooks.
Outside of Amazon.com, 4 other major online retailers comprise nearly the entirety of the remaining 26% of the US ebook market: the Apple iBookstore, the Barnes & Noble Nook store, the Kobo US bookstore, and GooglePlay Books.
At those 4 other stores, self-published indie ebooks make up 22% of all ebooks purchases and take in 32% of all author income generated by ebook sales.
Between 14% and 25% of all ebooks sold at Apple, Nook, and Kobo store lack Bowker-issued International Standard Book Numbers (ISBNs).
In total, more than 33% of all ebooks sold in the US each year have no ISBN.
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