Consumers made a few notable shifts in their book-buying habits in 2015, according to a new report, “Year in Books Review, 2015,” due out soon from Nielsen. The most pronounced change was in format preference. Unit sales of print books rose 2.8% in 2015 over 2014, according to figures from BookScan, while unit sales of traditionally published e-books fell 13%. The e-book figures are from PubTrack Digital, which tracks point-of-sale data from houses that Nielsen estimates account for 85% of unit sales of traditionally published e-books. (Nielsen owns both BookScan and PubTrack Digital.)

With the decline in e-book sales, the format fell to a 24% share of total books sold in 2015, down from 27% in 2014. E-books nevertheless had large market shares in certain categories, with Nielsen reporting that 60% of romance unit sales were for e-books; the format also accounted for 51% of unit sales of mysteries and thrillers. There was a huge discrepancy in the share of e-book sales in the major categories: e-books accounted for 48% of all fiction unit sales last year but only 2% of juvenile nonfiction sales.

Despite the drop in the sale of e-books, online retailers upped their share of book sales in 2015 over 2014. Based on responses to Nielsen’s Books & Consumers survey of book buyers, e-tailers represented 40% of unit sales last year, up from 35% in 2014. The finding is in keeping with reports from some major trade publishers that sales through online retailers have increased steadily in recent years; Penguin Random House, for example, said the online channel accounted for 50% of sales in 2015.

The growth in sales through the online channel came at the expense of bookstore chains and mass merchandisers. Independent bookstores, which have had a revival in recent years, increased their share of unit sales to 10% from 7% in 2014.

The decline in e-book sales from traditional publishers came in spite of—some observers would say because of—a steady increase in e-book prices. According to responses to the Books & Consumers survey, the median price of e-books bottomed out in the second quarter of 2015 and rose rapidly for the rest of the year, ending 2015 at about $10. Though e-book prices from traditional publishers rose last year, prices from self-publishers fell in the second half of the year, to about an average of $2.50 per copy.

The opposing trends in Big Five publishers’ e-book prices and self-publishers’ e-book prices fueled a decline in the Big Five’s share of e-book sales last year, which went from 38% in 2014 to 34% in 2015 (in 2012, the Big Five accounted for 46% of unit e-book sales). Self-publishers’ share of e-book sales rose to 12% last year from 8% in 2014 and from 5% in 2012. Small publishers’ e-book share, meanwhile, rose to 30% in 2015 from 26% in 2014 and 14% in 2012.

Some other observations Nielsen gleaned from its different sales-tracking services include an estimate that the share of Americans who bought books has fallen steadily each year since 2011, dropping from 53% in that year to 47% in 2015.

Many Americans who bought books last year bought adult coloring books. According to Nielsen, a total of 12 million coloring books were sold in 2015, up from one million in 2014, with the spike due to the adult coloring book phenomenon; 71% of adult coloring book buyers were women.

One area that has remained relatively unchanged in recent years is book discovery. The most common way book buyers found a print book was by browsing in a store, and looking through an e-tailer’s site was the most common method buyers used to find an e-book.