The list price for the bestselling book "H is for Hawk" is $26. The price is printed right on the inside jacket. And that's what the nonfiction hardcover sells for at The King's English Bookshop in Salt Lake City, Utah.

The same book sells for $15.60 at Amazon.

Amazon has been discounting books for so long that it hardly surprises. Readers expect it from the online retailer. It's why Amazon has become the largest single mover of books in the U.S.

But now a coalition of U.S. booksellers and authors has asked the U.S. Department of Justice to investigate how Amazon conducts business. The group Authors United wrote requesting an antitrust inquiry into how the retailer came "to dominate a venue for communication." Amazon's practices have hurt the interests of America's readers and the overall book industry, the group said in a letter to the Justice Department that it says was received Monday.

The American Booksellers Association also wrote to the Justice Department to offer its support for the antitrust inquiry, accusing Amazon of predatory selling by offering book titles at what appears to be below-cost  and employing strong-arm tactics when a publisher fights back. Last year, publisher Hachette entered into a contentious dispute with Amazon over the profit split from its e-books. At one point, Amazon blocked pre-orders of books by Hachette authors such as James Patterson. The two sides settled late last year.

Publishers typically charge booksellers about 50% of the list price. Amazon sells "H is for Hawk" at a 40% discount, meaning Amazon likely still turns a small profit, depending on the specific arrangement it has with the publisher. However, small booksellers say they can not afford to offer such widespread and consistent discounts.

Justice Department said it was too early to comment on the antitrust request.

“We look forward to reviewing the materials they have provided,” spokesman Peter Carr said.

Amazon did not respond to a request for comment. Jeff Bezos, CEO of Amazon, owns The Washington Post.

The complaints from booksellers and authors centers on how Amazon's low prices hurt free expression and the health of the U.S. book industry.

Last month, European Commission regulators said they were investigating Amazon's pricing of e-books. These are the same regulators that are looking into whether Google violated antitrust rules by directing users of its Web search to the company’s own products.

With Amazon, European regulators are examining whether Amazon struck e-book deals that make it harder for its competition.

Concern for business competitors --  rather than just consumers -- is one consistent difference between regulators in the U.S. and Europe.

Readers in the U.S. are paying less for books, thanks to Amazon. That would not appear to be harmful. But the complaint from booksellers and authors argues that something else is being lost in the process.

"It's so galling," said Betsy Burton, president of the American Booksellers Association, who has run The King's English Bookshop for 37 years. "They are using books as loss leaders to sell more -- I don't know -- washing machines. Amazon sees books as products. I've never thought of books as products."

So she sells "H is for Hawk" for $26 and hopes the consumer is willing to spend more.

"It comes down to purely price," she said. "That's the problem right there."