It's getting complicated in the world of publishing.

Unlike last year, the top-selling books in print and those in digital are rather different, according to a story in Publishers Weekly reporting on sales during the first six months of the year. While Dan Brown's "Inferno" tops both the Bookscan (a Nielsen service that tracks purchases at point of sale) and Amazon Kindle best-seller lists for the first half of 2013, 15 of the 20 books on each list are different.

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"Proof of Heaven," a nonfiction title from a neurosurgeon who claims to have made a round-trip visit to the afterlife during a near-death experience, is second in Bookscan numbers but missing entirely from the top 20 Amazon Kindle best-sellers. "Lean In," Sheryl Sandberg's treatise on women and corporate leadership, was absent from the digital best-sellers but fourth in print sales.

The Kindle best-sellers include three self-published writers: Colleen Hoover, Elizabeth Naughton and H.M. Ward. Their books barely register in the print sales figures.

It looks to me as though people who read digitally (mostly on Kindle devices) and those who prefer print are shopping in fundamentally different "stores" and being exposed to different books. Amazon has created a kind of ecosystem that keeps readers buying books that are aggressively priced or "recommended."

There's some obvious upside to this. Self-published writers stand very little chance of being stocked in a Barnes & Noble. Using open access to the Amazon ecosystem, entrepreneurial authors can become best-sellers without any help from the traditional publishing system of agents, editors, publishers and distributors. When a success breaks out of the pack, certain titles can go viral.

I have worries, though. These trends increase the commoditization of books, and one book becomes as useful as the next in generating a fee-gathering download. The "best" books are the ones that sell the most. We know that high sales and quality do not necessarily intersect.

While I accept that the exchange of money for product makes books a kind of commodity, I also believe they are something more meaningful. Books are a repository of our culture. They hold meaning and importance greater than their utility to extract money from consumers. For more than a century, the market inefficiencies of traditional publishing protected "literature" from commerce. Publishers were literally family-owned businesses that viewed publishing good books as a responsibility, which led them to subsidize and produce books that otherwise might never have existed.

Newspapers used to run under this model as well.

The old system's success is evident in one of the best-selling books of the first half of 2013, a fresh new title called "The Great Gatsby." "Gatsby" was initially published by Charles Scribner's Sons in 1925 to solid acclaim but limited sales. Scribner's kept the book in print, believing it to be important. Scribner is now an imprint under one of the "Big 5" publishers, Macmillan, which is in turn a subsidiary of Holtzbrinck, which has offices in dozens of countries.

"The Great Gatsby" sells 500,000 copies a year. Good art and good business. In the future, will there still be room for books that might not make money in the short term? The new ecosystem is a boon to many, but we shouldn't pretend that it doesn't come with costs.

Biblioracle John Warner is the author of "The Funny Man." Follow him on Twitter @Biblioracle.

The Biblioracle offers his recommendations

1. "The Man With the Golden Arm" by Nelson Algren

2. "We Live in Water" by Jess Walter

3. "Freedom" by Jonathan Franzen

4. "The Lazarus Project" by Aleksandar Hemon

5. "To Show and to Tell" by Phillip Lopate

— Frank T., Chicago