If J.K. Rowling's new web store proves a success, it could provide a model for other authors and publishers and undermine the clout of Amazon.com Inc.

When the Harry Potter books finally went on sale in electronic form on March 27, it was as if Harry himself had cast the “Alohomora” spell on them—the one that unlocks doors: In a break with industry practices, the books aren’t locked down by encryption, which means consumers can move them between devices and read them anywhere they like.

If “Pottermore,” J.K. Rowling’s new web store, proves a success, it could provide a model for other authors and publishers and undermine the clout of Amazon.com Inc., which now dominates eBook sales.

“I think it’s a very large crack in a dam that’s going to collapse in the next nine to twelve months,” says Matteo Berlucchi, the CEO of an independent British-based online bookstore, aNobii.

eBooks from major publishers are sold in encrypted form today. The text of a book is scrambled so that only authorized devices and software can read it. For instance, a book bought from Amazon can be read only on the company’s Kindle eReaders and on its Kindle applications for smart phones, tablets, and PCs. It can’t be read on Barnes & Noble’s Nook eReaders.

Conversely, a book for the Nook can’t be read on a Kindle. A book purchased from Apple Inc. can only be read on iPhones, iPod touches, and iPads.

Publishers insist on encryption in the form of “Digital Rights Management,” or DRM, because they believe it stops piracy. It also helps eBook retailers like Amazon defend their business models, keeping non-Amazon books off Kindle eReaders.

But when Rowling fans buy a book from Pottermore, they can download it in a variety of formats, including one that is not protected by DRM. They can be read by a wide variety of applications and devices.

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These books can be purchased once and then passed around to friends or shared with children. Wider sharing is dissuaded by visible and invisible “watermarks” inserted by Pottermore before the download, which identify the buyer.

Charles Redmayne, CEO of Pottermore, says that “Harry Potter” books are probably the most pirated in the world already, even though—or rather, because—there have been no legal electronic versions until now. Fans have scanned or even retyped the printed books to make them available in electronic form.

“We believe that people should have the right, once they’ve bought the book, to read it on any device that they chose to,” says Redmayne.

Of course, there’s another reason Pottermore is going DRM-free. It wants to “own” the relationship with the customers—the Potter fans—rather than have them go to other retailers. And the only way to get onto all reading devices without dealing with the other retailers is to sell books without DRM.