J.K. Rowling, who ignited a new generation of readers with her series of seven boy-wizard novels, launched the next transformative chapter in how and where books will be distributed by unveiling her own online store that will sell Harry Potter e-books directly to her fans.

In a video address to readers, Ms. Rowling said she created her own Harry Potter universe for fans to visit online. While her publishers and major online book retailers will continue to sell her physical books, Ms. Rowling has reserved for herself the digital editions, the fastest-growing segment in the book world.

British author J.K. Rowling is pictured with a child during the announcement of Pottermore in London on June 23. EPA

The move could inspire other authors, large and small, to pronounce themselves independent agents in hopes of tapping more lucrative paydays. Ms. Rowling refused for years to release her books in electronic format, retaining the digital rights for herself.

While most other authors have already handed over their digital rights to their publishers—most recently, John Grisham—Ms. Rowling's deal could prompt them to self-publish when their deals come up for renewal or demand higher royalty rates than the 25% of net sales that most publishers offer today on digital editions.

Some may even choose to forgo all traditional means of book publishing and set up their own bookstores, reaping 100% of everything they sell.

"Every writer watches with great interest whenever somebody does something new," said best-selling author Jennifer Weiner, whose next book, "Then Came You," goes on sale July 12. "We all pay attention. If this turns out to be a success for her, for an author who had unheard-of success by selling through traditional bookstores with books on paper, then some may decide that they, too, don't need bricks-and-mortar stores, or online booksellers, either."

Ms. Rowling, 45 years old, will launch a test version of her Pottermore website on July 31 and begin selling e-books in October. All seven Harry Potter novels will be available as e-books in multiple languages and will be device agnostic.

Hogwart fans, try to hold in your excitement: Harry Potter mastermind J.K. Rowling is finally taking the digital plunge, launching an online store that will sell Harry Potter e-books directly to consumers.

Though she says she won't be writing any more Potter books, Ms. Rowling is emptying her extra material into various corners of the site. She has handed over 18,000 words of additional content so far but says she will write more for the site as well.

The British author said Thursday she is lucky to have the resources to go straight to readers—and is happy she can ensure they have an equally magical experience when interacting with the digital Harry Potter. "There was really no other way to do that, for the fans or for me, other than to just do it myself," she said.

Ms. Rowling's declaration of retail independence comes at a time of extreme turmoil in book publishing and retailing around the world. In the year ended April 30, U.S. e-book sales jumped 163% to $313 million, according to the Association of American Publishers, but the sale of adult hard-cover books declined 19% to $300 million. The figures reflect the reporting of 22 companies.

Five years ago, an author such as Ms. Rowling wouldn't have had the tools to sell her own works globally by herself.

The issue of ownership of digital works has emerged as the most explosive in publishing today. Several start-up digital publishers are luring authors and estates by offering twice the royalty compensation on digital works compared with traditional publishers.

Harry Potter series sales across different media

Publishers are intent on holding the line on both rates and rights. Most dramatically, they have repeatedly said they won't sign contracts and offer advances to authors without acquiring all digital rights. But as companies such as Amazon.com Inc. AMZN 0.12% increase their own publishing efforts, the traditional publishing world is coming under greater pressure to keep their authors happy.

The risk Ms. Rowling runs—the possible retaliation by retailers toward her next titles—appears limited compared to the potential financial rewards and her ability to control her relationship with her fans the way she wants. The ability to shape all forms of the book-selling and marketing experience has been a lifelong dream for many authors over the ages.

Such a step won't be for all authors, however. Best-selling writer James Patterson, who in 2009 signed a 17-book contract with Lagardère SCA's Hachette Book Group, said that while he has mulled "the notion of having my own book company," he has decided "life is too short."

Mr. Patterson said he thinks a certain number of authors will be eager to try more innovative forms of publishing,whether it be best-selling authors or those trying to build an audience. "Many people are going to be trying to figure out how to break into the game," he said. "But I don't want to do something that might be disruptive to the publishing industry. And I'm protective of independent bookstores."

The news received a mixed response from book retailers. The U.K.'s biggest chain, Waterstone's, issued a statement expressing its "disappointment" at being shut out of the digital launch and noting that it had been a "key factor in the growth of the Harry Potter phenomenon since the first book was published."

But in the U.S., Barnes & Noble, the nation's largest bookstore chain, actively promoted Potter titles on its website on Thursday via a link to Ms. Rowling's video announcement of the Pottermore site and said it would work to make Potter e-books available on its Nook reading device.

A spokeswoman for Amazon said, "We're working closely with Pottermore to make sure Kindle customers will be able to buy and read J.K. Rowling's Harry Potter books." An Apple Inc. spokesman had no comment.

Ms. Rowling has built the Potter franchise into a behemoth since the first of her Harry Potter novels was published in 1997. The series has sold about 450 million books world-wide, and spawned an eight-part film franchise for Time Warner Inc.'s Warner Bros. that concludes in July, around the time of the initial Pottermore launch. In 2010, Forbes magazine estimated Ms. Rowling's net worth at $1 billion.

Bloomsbury Publishing BMY 2.84% PLC owns the British print rights to Harry Potter, and Scholastic Corp. SCHL 1.01% owns the printrights in the U.S.

Ms. Rowling isn't entirely pushing aside her publishers. Bloomsbury and Scholastic both said in statements Thursday that they would receive a cut of Pottermore's e-book sales. "It is because J.K. Rowling wanted to be in a partnership with her print publishers on this project," a Bloomsbury spokeswoman said. Both Bloomsbury and Scholastic said they would provide marketing and promotional support for the Pottermore site.

The decision to release the Potter books digitally comes at a time when there is increased speculation about which formats—physical or digital—children will embrace in the years ahead. Scholastic, for example, is currently working on an e-reading software application for kids that is designed to bolster digital reading and that will likely be unveiled this fall.

Pottermore is a Harry Potter online world that allows readers to join one of the Hogwarts wizardry school's four houses and travel virtually through the first Harry Potter book. Along the way, members encounter extra material Ms. Rowling has written or unearthed from her notes, giving intense Potter fans much-desired insider explanations of key characters, places and plots. Users receive their own magical wands and home pages—and can do things like post drawings and challenge one another to wizard duels.

Among extra material, Ms. Rowling says she kept the back story of Professor McGonagall—headmistress of Hogwarts—for years expecting to use it, but never found a place for it in any of the books.

"I had half of the new material already written or in note form," Ms. Rowling said Thursday. "I dug some of it out of boxes, literally."

Sony Corp. partnered with Ms. Rowling on developing the site and plans to sell branded Pottermore products, such as e-readers, out of the online store.

Write to Jeffrey A. Trachtenberg at jeffrey.trachtenberg@wsj.com and Paul Sonne at paul.sonne@wsj.com