Originally Posted by fjtorres
The most recent numbers for the US marketplace with some credibility come from the NYT piece on B&N that quotes Amazon share at 60%-plus. With B&N itself claiming 27% and Kobo claiming 8%, that leaves maybe 5% for iBooks and the Adept crowd.
Until better numbers come out, those will have to serve.
The last figure I remember from Apple was 180,000,000 iBooks downloaded (not purchased) during the first 9 months of 2011. They may have ended the year with 240 million, if rate continued. If Apple has less than 5% that would mean over 6 billion ebooks downloaded last year. Possible, I suppose. Or more likely Apple has a greater than 5% share and when you add in Sony, Google, BoB, Diesel, Smashwords and the others it's a higher probability. That throws off the other figures.
The OP asked about ereaders so the above doesn't answer or help him any.