See the interesting article:
22 September 2015 – The Plot Twist: E-Book Sales Slip, and Print Is Far From Dead
Media New York Times
By ALEXANDRA ALTER
New York Times

Some of the interesting facts, read the full article for all details:

E-book sales soared, up 1,260% between 2008 and 2010, alarming booksellers; print sales dwindled, bookstores struggled to stay open. Analysts once predicted that e-books would overtake print by 2015 but digital sales have instead slowed sharply. E-book sales fell by 10% in the first five months of 2015. Digital books accounted in 2014 for around 20% of the market, roughly the same as they did a few years ago.
Sales of dedicated e-reading devices have plunged as consumers migrated to tablets and smartphones. And according to some surveys, young readers who are digital natives still prefer reading on paper.

Independent bookstores are showing strong signs of resurgence. The American Booksellers Association counted 1,712 member stores in 2,227 locations in 2015, up from 1,410 in 1,660 locations five years ago.
The big publishing houses are pouring money into their print infrastructures and distribution. Most booksellers agree that they are witnessing a reverse migration to print.

Some 12 million e-readers were sold in 2014, a steep drop from the nearly 20 million sold in 2011, according to Forrester Research. The portion of people who read books primarily on e-readers fell to 32% in the first quarter of 2015, from 50% in 2012, a Nielsen survey showed.
Higher e-book prices may also be driving readers back to paper. With little difference in price between a US$13 e-book and a paperback, some consumers may be opting for the print version.
It is also possible that a growing number of people are still buying and reading e-books, just not from traditional publishers. The declining e-book sales reported by publishers do not account for the millions of readers who have migrated to cheap and plentiful self-published e-books, which often cost less than a dollar.

At Amazon, digital book sales have maintained their upward trajectory. In 2014 Amazon, which controls some 65% of the e-book market, introduced an e-book subscription service that allows readers to pay a flat monthly fee of US$10 for unlimited digital reading. It offers more than a million titles, many of them from self-published authors.