He would not say how many were downloads of free books. Selections at the iBookstore were greatly improved this year when Random House Inc., publisher of Stieg Larsson and John Grisham, among others, agreed to sell through Apple after resolving differences over pricing.

Brian Murray, CEO of HarperCollins Publishers, said iBookstore sales were “a little smaller than expected,” but he praised the iPad as a multimedia breakthrough that enabled publishers to sell electronic picture books and “enhanced” eBooks that include video and sound.

“There are certainly areas for improvement, as there are with every book retailer and device,” he said. “But the promise of having another platform where books can be discovered is still true today. The potential is enormous.”

A strong No. 2 to Amazon has emerged, but it’s Barnes & Noble, which launched the Nook late in 2009 to skepticism about everything from the name “Nook” to the design.

New York Times technology writer David Pogue had mocked the Nook’s “half-baked software” and called the device “an anesthetized slug.”

But Barnes & Noble has worked to improve the Nook and to offer different types, including a touch-screen version announced this week. The company promoted the Nook relentlessly through its superstores and now has around 25 percent of eReader sales, publishers say.

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