Robbie Trencheny, an 18-year-old high school senior in Danville, Calif., loaded half a dozen textbooks and novels into his Nook digital reading device as soon as he received it as a birthday present from his parents last week.

"I don't have to carry textbooks with me anymore," said Trencheny, who also bought a few books on the device for leisure reading. "Plus, e-books are cheaper than most normal books."

But Trencheny was one of the lucky ones.

Barnes & Noble Inc.'s Nook reader, which can hold 1,500 digital books, was sold out in early December, and anyone ordering it now is not expected to receive it until February.

One of the hottest gadgets of the year is already in short supply. And despite a flurry of announcements in recent months, shoppers are finding more hype than products on store shelves.

While sales of Amazon.com Inc.'s Kindle readers continue to sizzle, other manufacturers are either late to the party or delaying their product launches until next year.

IREX Technologies, a European spin-off of Royal Philips Electronics, said its device, which had been slated to come out in the fall, had run into "unexpected delays."

Barnes & Noble eked out its Nook in December but had only enough to send out to customers who had preordered the device online earlier in 2009.

Sony Corp. announced its Daily Edition wireless touch-screen reader in August but did not start shipping the device until a couple of weeks ago. For customers who preordered the $400 Daily Edition, the Japanese consumer electronics giant rushed them out by priority mail in time for Christmas. But finding them in stores now is highly unlikely.

"What's announced, what's rumored to come, and what's available are three different things," said Ned May, an analyst with Outsell Inc.

Readers are snapping up what's available at a rapid pace. Sales of e-readers have tripled from 1 million units in 2008 to an estimated 3 million in 2009, according to technology consulting company Forrester Research. Close to one-third of those sales were expected to occur between Thanksgiving and tomorrow.

Amazon, which entered the market in 2007 with its Kindle reader, said the $259 device was the company's No. 1-selling item across all categories in November. The Seattle Web merchant did not disclose how many Kindles it had sold.

Driving sales is the convenience of being able to have hundreds of books in a device the size of a slim paperback. Some devices, such as the Kindle, Nook and Daily Edition, let readers buy digital titles via wireless connections to the Internet, without having to plug into a computer.

Those who have walked away empty-handed this holiday, however, should not feel unlucky.

Next year will bring a wider array of choices, more fancy features, and very likely lower prices, analysts predict.

A number of companies are holding off their product launches until January's Consumer Electronics Show in Las Vegas. One company, Plastic Logic, said it would show a shatter-resistant touch-screen reader that's the size of a sheet of notebook paper.

Entourage Systems Inc. is expected to unveil a device that has two types of screens. One is a color touch screen similar to Apple Inc.'s iPhone. The other is a gray-scale E Ink screen, the same technology used by Sony, Barnes & Noble, and Amazon. The Entourage device is meant to offer the best of both screen types, including the bright color screen of an LCD and the low power consumption of an E Ink screen, which can go for as long as two weeks on a single charge.

A different type of device, called a "mini-tablet," also may emerge next year. Essentially bigger versions of Apple's iPod Touch, these high-resolution, color touch-screen tablets allow users to browse the Web, flip through photos, read books and articles, play games or watch video.

Prices are likely to come down next year. Already, Amazon has scaled back the price of its Kindle 2 from $359, when it was first introduced in February, to $259. Sony this year began selling a basic model for just under $200.

Another reason for shoppers to wait: Book publishers, which have released hundreds of thousands of titles for sale on these devices, may start holding back some titles for fear that digital sales could cannibalize more lucrative hardcover book sales. Amazon, Sony and Barnes & Noble, for example, price best-sellers about $10 for each digital copy, whereas hardcover versions still go for about $25.

"The reason these devices sell so well is because they can get the New York Times 100 best-sellers," said James McQuivey, a Forrester Research analyst. "But what happens when publishers hold back the digital versions?"

New York publisher Simon & Schuster Inc. did just that this month when it announced that it would hold off releasing digital versions of 35 major book titles for four months after the hardcovers debut.

Two other publishers, Hachette Book Group and HarperCollins Publishers, followed with announcements that they would begin delaying e-book versions of their titles starting next year.

A final reason for consumers to pause before snatching up the first e-reader they can find: Not every device gives users access to the same selection of books.

The Nook is tied to Barnes & Noble bookstore, while Kindle dials up Amazon's Web site. Sony's device is linked to its online bookstore and is designed to let owners easily borrow books from many public libraries, something the Kindle doesn't do.

As a result of the copy protection measures each company deploys, books bought in one bookstore may not be displayed on another store's device. Nook owners, for example, cannot read copy-protected digital books purchased from Amazon.

"These devices are essentially little dedicated vending machines that people buy so they can purchase books from one store," said Ross Rubin, executive director of industry analysis with NPD Group Inc.