Free online textbooks are increasingly being sold on Amazon, and it appears to be a hot seller for the e-book industry.

A study published Monday by the consulting firm eMarketer found that more than half of all textbooks sold on the Amazon Marketplace this year are free.

The study also found that about 35% of textbooks sold through the site were free.

The eMarketers study found that 51% of books sold through Amazon were free, compared to 34% in 2014.

It also found more than 1 million free textbooks were sold this year, up from 647,000 in 2014, a jump of more than 60%.

The study noted that the rise of free online textbooks has been largely driven by the demand from publishers who want to give students a wide array of materials in an online learning environment.

The study also noted that more and more students are enrolling in online classes at universities and colleges.

The increase in enrollment is also expected to continue this year as students graduate from college.

The online textbook industry has become a major source of income for publishers and for the textbook industry, as publishers and universities seek to expand their offerings online.

It is estimated that about 15% of the global book market is in the form of free books, which includes eBooks, eTextbooks, and e-textbooks.

The report also found eBooks accounted for more than a third of all sales on Amazon.com this year.

The total number of books that were purchased through the marketplace this year totaled 1.6 million.

The market share for eBooks is expected to reach 17% of all e-books this year by the end of 2019, up slightly from 17% in 2018.

The overall number of eBooks sold in 2019 was 1.2 million, up 1.5% from the previous year.

Amazon’s share of the total e-commerce market in 2019 is expected at around 9%.