It has been taken on faith by many, including your benighted scribe, that the future of book publishing is digital, that the e-book will displace the printed codex as the dominant form of the dominant artifact of modern culture. There have been differing views about how fast the shift will happen (quite a few people believe, mistakenly, that it has already happened), and thoughts have varied as well on the ultimate fate of printed books—whether they’ll disappear entirely or eke out a meager living in a mildewed market niche. But the consensus has been that digitization, having had its way with music and newspapers and magazines and photographs and etc., would in due course have its way with books as well.

In my last post, on the triumph of the tablet over the e-reader, I noted the release of a new Pew study on Americans’ reading habits. The title of the report — “E-book Reading Jumps; Print Book Reading Declines” — nicely encapsulates, and reinforces, the common wisdom. But if you dig deeper into its pages, you find indications that the picture is not as clear-cut as that title suggests. For one thing, the printed book remains, by far, the preferred format for American book readers. Fully 89 percent of them report that they read at least one printed book over the preceding 12 months. Only 30 percent say they read at least one e-book — a percentage that, perhaps tellingly, has increased by only a single point since last February, when the survey was last conducted. The study did find that the percentage of American adults who read e-books increased over the past year, while the percentage that read printed books fell, but the changes are modest. E-book readers rose from 16 percent to 23 percent, while printed book readers declined from 72 percent to 67 percent. (The survey’s margin of error is 2.3 percent.) Yes, there’s an ongoing change in reading habits, but it no longer looks like a sea change.

A lot of other data came out during the course of 2012 that also suggests that (a) the growth in e-book sales has slowed substantially and (b) print sales are holding up pretty well. At a conference in March, Bowker released market research showing that, even though just 20 percent of American web users have actually purchased an e-book, e-book sales growth has already “slowed dramatically” from the explosive levels of the last few years and is now settling down at an “incremental” rate. There are, reports Bowker, signs of “some level of saturation” in the e-book market, and, strikingly, the heaviest buyers of e-books are now buying more, not fewer, printed books. The Association of American Publishers recently reported that annual growth in adult e-book sales dropped to 34 percent during the first half of 2012, a sharp falloff from the triple digit gains of the previous few years. As of August, e-book sales represented 21 percent of total sales of adult trade books. While e-book sales seem to be eating away at mass-market paperback sales, which have been falling at around a 20 percent annual clip, hardcover sales appear to be holding steady, increasing at about a 2 percent annual rate.

Big publishers have also been reporting a sharp slowdown in e-book sales growth, with a Macmillan representative saying last month that “our e-book business has been softer of late, particularly for the last few weeks, even as the number of reading devices continues to grow.” It’s hardly a surprise that the growth rate of e-books is dropping as the sales base expands — indeed, it’s inevitable — but the recent decline seems considerably more abrupt than expected.

Children’s e-books were growing at a strong 250 percent clip early last year (from a much lower base), but printed children’s books were also showing strong growth, with hardcover sales rising at an annual rate of nearly 40 percent. In fact, the total sales growth of printed children’s books exceeded that of electronic copies. Meanwhile, printed books showed strong sales over the holidays, with unit sales in the U.S. up 5 percent over 2011 levels. In the U.K., sales of printed books reached their highest level in three years during the week before Christmas. Combine all these numbers with the fact that sales of dedicated e-readers are falling sharply, and suddenly it seems possible that reports of the death of the codex may have been exaggerated.

So why might e-books fall short of expectations? Here are some possibilities:

1. We may be discovering that e-books are well suited to some types of books (like genre fiction) but not well suited to other types (like nonfiction and literary fiction) and are well suited to certain reading situations (plane trips) but less well suited to others (lying on the couch at home). The e-book may turn out to be more a complement to the printed book, as audiobooks have long been, rather than an outright substitute.

2. The early adopters, who tend also to be the enthusiastic adopters, have already made their move to e-books. Further converts will be harder to come by, particularly given the fact that 59 percent of American book readers say they have “no interest” in e-books, according to the Bowker report.

3. The advantages of printed books have been underrated, while the advantages of e-books have been overrated.

4. The early buyers of e-readers quickly filled them with lots of books, most of which have not been read. The motivation to buy more e-books may be dissipating as a result. Novelty fades.

5. The shift from e-readers to tablets is putting a damper on e-book sales. With dedicated readers, pretty much the only thing you can do is buy and read books. With tablets, you have a whole lot of other options. (To put it another way: On an e-reader, the e-reading app is always running. On a tablet, it isn’t.)

6. E-book prices have not fallen the way many expected. There’s not a big price difference between an e-book and a paperback. (It’s possible, suggests one industry analyst, that Amazon is seeing a plateau in e-book sales and so is less motivated to take a loss on them for strategic reasons.)

None of this means that, in the end, e-books won’t come to dominate book sales. My own sense is that they probably will. But, as we enter 2013, I’m considerably less confident in that prediction than I was a few years back, when, in the wake of the initial Kindle surge, e-book sales were growing at 200 or 300 percent annually. At the very least, it seems like the transition from print to electronic will take a lot longer than people expected. Don’t close that Gutenberg parenthesis just yet.

UPDATE: A new version of this post was published as an article in the January 5 edition of the Wall Street Journal with the headline “Don’t Burn Your Books — Print Is Here to Stay.” (The headline writer is a bit more definitive in his assessment than I am, but that’s not unusual.)