Here's one good reason why you may want to take the hardcover of David Sedaris' new book to the beach this summer instead of the digital version for Amazon's Kindle: Sand between the pages won't ruin a good story.

About six months after its introduction, the Kindle electronic reading device is entering its first beach season amid increasing discussion that the gadget may have a future.

Skepticism about whether people will try reading books on a screen instead of the printed page is being joined by evidence of a nascent but growing market for the Kindle and its competitor from Sony.

Much of the talk focuses on the comment by Jeff Bezos, Amazon's founder and chief executive, who said for the first time that the Kindle is having an impact on book sales.

"Of the 125,000 books available both as a physical book and on Kindle, Kindle books already account for over 6 percent of units sold," Bezos said in a statement coinciding with a book-publishing trade show in Los Angeles.

On the other hand, Amazon won't disclose how many consumers have bought a Kindle — now selling at $359, reduced from the original $399 — or how many actual e-books have sold for the device.

Nonetheless, publishers are making more titles available on the Kindle. Simon & Schuster Inc. said it would add 5,000 titles to its Kindle offerings after e-book sales grew by 40 percent in 2007.

E-books represent the fastest-growing category for publishers, though the sales volume is tiny compared to traditional books. In 2007 sales rose by 23.6 percent over 2006, accounting for $67 million in sales.

Overall, the book industry grew by 3.2 percent in 2007 and had sales of $25 billion, according to the Association of American Publishers.

Ross Rubin, an analyst for the NPD Group, said it's still too early to say if e-books will have a big impact on book sales, but the category is emerging.

"There are only two players, and publishers are just starting to open up their catalogs," he said. The other player is the Sony Reader Digital Book.

Rubin said the Sony product had a "decent holiday season" last year and that the $299 device has some form-factor advantages over the Kindle. "It's a thinner and simpler product in some ways," he said. NPD is tracking sales for the Sony device, but it won't disclose details.

For small publishers, the Kindle can provide a new outlet for sales.

"I think for small presses such as ours, whose books are often not available as readily, something like Kindle may actually increase sales," said Donna Shear, director of Northwestern University Press.

"The groundswell has shifted among small presses, who for years might have resisted electronic publishing," she said. "The physical book is not going to go away, but this is another viable delivery system, and we have to think of it as an opportunity and not a threat."