By Alistair Barr

(Reuters) - Amazon.com Inc and Barnes & Noble Inc unveiled Harry Potter e-books on Tuesday in deals that suggest the companies made big concessions with author J.K. Rowling for electronic access to the hit series.

Amazon said it struck a distribution deal with J.K. Rowling's new website pottermore.com.

Amazon customers can search for the Harry Potter e-books in the company's Kindle Store, but will be directed to the Pottermore Shop to register and buy them, then add the titles to their Kindle library, the company said.

Users of Amazon's Kindle e-readers and Kindle Fire tablet will be able to read the e-books through those devices and through applications on other devices.

Barnes & Noble made a similar announcement, saying that customers of its Nook e-readers and tablets can buy Harry Potter e-books through the Pottermore Shop.

Sending customers away from Amazon.com and Barnes & Noble's website is a big concession for the companies because J.K. Rowling's Pottermore site will be able to collect customer information and credit card details. This is valuable information that e-commerce companies usually carefully guard.

"They are her customers now. She knows about them because they have registered with her site," saidMike Shatzkin, head of digital publishing consulting firm The Idea Logical Company. "It's a huge concession. Amazing."

BEATLE POWER

The popularity of Harry Potter means J.K. Rowling likely had more leverage than other authors with companies like Amazon, he added.

"J.K. Rowling is the Beatles," Shatzkin said. "Amazon decided that having the Potter books to sell was more important than the control they usually insist on."

This suggests that publishers may struggle to negotiate similar e-book deals for other authors with retailers, he added.

Jim Friedland, an analyst at Cowen & Co, said Amazon likely accepted a smaller cut of the sale price of the Harry Potter e-books. The usual share is 30 percent, while Amazon likely accepted 20 percent or 10 percent, the analyst noted.

Despite that, there is little extra cost for Amazon to sell Harry Potter e-books this way. The deal may also encourage more readers to buy Kindle devices, Friedland said.

Foreign-language versions of the Harry Potter e-books will be available through Kindle Stores worldwide in coming weeks, Amazon added.

The Potter e-books are compatible with other digital platforms including Sony's Reader and Google'sPlay, Pottermore said in a statement.

"Not only is this phenomenally popular series available in eBook form for the first time, but across an extensive range of devices and platforms, thanks to unique collaborations with leading online retailers," Pottermore CEO Charlie Redmayne said

(Reporting By Alistair Barr; Editing by Gerald E. McCormick, Phil Berlowitz)