For changes in ebooks sales, rather than the reading technology, this rather dated page is interesting
http://idpf.org/about-us/industry-statistics
It's clear (ignoring the dodgy curve fitting!) that ebook sale rose fairly steadly but slowly (apart from a dip in second half of 2005) until 2008, and then went up lots.
If the graph continued to 2014, judging by
AAP's number for 2014, it would be showing quarterly sales of around $500 million (wholesale).
And so yes, your perception that the big change in ebook sales happened between 2008 and 2013 is probably true. That's when ebook sales went from being an insignificant part of the total market to a major part, if not quite yet the majority of book sales.