Despite the Kindle's continuing success, it's widely believed that the device cannot remain simply a terminal for Amazon's (AMZN) e-book sales if it is ever to become a true mass-market product. But what must it become? Some leading figures in the publishing business insist that sales growth in digital publishing will come only when e-books are incorporated into an all-purpose communications device like the iPhone.

Since February, however, the combination of unexpected sales growth for Kindles at Amazon, including the release of a larger, more versatile reader—the Kindle DX—has begun to suggest that we may be moving in the opposite direction, toward a highly specialized reading-centric device.

Amazon isn't alone in this ambition. The imminent launch of the Plastic Logic product and rumors that Hearst is far along in creating a new reading service that will support a broad range of content makes that trajectory more plausible.

With this in mind, I persuaded the folks at Plastic Logic to give us a preview of their product. At the same time, Amazon graciously provided me with a Kindle DX.

First, I should come clean about my own hopes and expectations for these devices. In many ways, I'm the ideal consumer for a reading platform. I read a lot of books and periodicals and, for a number of years, I've been keenly exploring how writers could benefit from digital distribution. So I can be accused of having hopes for these readers that are too high.

The CEO of one big publishing company says that books will be at an advantage for being the last major medium to be digitized. But I fear consumers who have become accustomed to digital content that is breathtaking on the Internet (and pretty good on their smartphones) will have less patience with the limitations of these E Ink-based devices. For example, everyone asks when E Ink will support color, but machines have still not mastered basic black and white.

So let's not focus on bells and whistles. I am interested in a highly efficient reading machine. The Internet is great for collapsing time and space. Reading has become a digger's dream of sources and resources. But the computer is a lousy place to consume all of that wonderful content. What I've wanted was an electronic dossier where—at a minimum—I could sweep all those PDFs downloaded from the Web and save them for convenient reading. If that dossier also gave me access to newspapers, magazines, and a boatload of books and reference material, I'd be in wonk heaven.

When the first Kindle was announced, I knew there would be no great leverage to come from being an early adopter. Too many kinks needed to be worked out. Then the Kindle 2 was launched. I got tempted but had already heard about the Plastic Logic device and seen their demo; I knew Amazon wasn't supporting PDFs and that was a nonstarter for me.

Unlike the first Kindles—which draw their power from the allure of books—Plastic Logic is coming at the reader market from the opposite direction. It sees itself as building a device for the bulging-briefcase crowd: anyone who has to wade through long documents. We're talking about lawyers and management consultants, stock analysts, bankers, and marketing directors. These people want something that allows them to riffle through stacks of paper to get to the ones they want; annotate, store, and carry documents; maybe take a break and read something from the press; or, God forbid, relax with a novel.

To appeal to these middle-management types, Plastic Logic built a large (about the size of an 8½-by-11 pad), lightweight device with only one button. That's an on/off switch. You navigate by touching the screen. In all other respects, the reader—which will have a different, yet-to-be-revealed name when it launches in early 2010—is very similar to the Kindle DX, which just started shipping in mid-June.

Both devices use the same E Ink-screen technology, which displays the page in dull gray that looks like soggy newsprint and has a tendency to show through the last image.

That's indoors. In brighter light, the E Ink screen seems closer to white and generates enough contrast to make the print seem crisp and dark. Amazon has cleverly created a bright white case around its Kindles, no doubt to enhance the whiteness of the E Ink screen. As a result, the case is easy to smudge with fingers that are anything less than pristine.

In moving to the larger PDF-friendly platform, the good people at Amazon have gotten ahead of themselves. It's not fair to judge the Plastic Logic folks on a demonstration system, but it would appear that their user interface is no better than Amazon's. It took me a few days to invent my own system for selecting PDFs and transferring them to the Kindle. Amazon should have done that for me, no?

The Internet has plenty of content aggregators; I no longer spend my mornings scanning the newspapers. Instead, I flit from aggregator to aggregator, alighting on stories to read. The stuff that looks promising gets copied in PDF form and saved to my desktop. With the Kindle, I found that I could tweak my printing protocol to save the PDFs directly to the Kindle's document folder. Unfortunately, when I finally grabbed a seat on the train and flicked my Kindle to "on," the document screen was a random mess of stories that I could barely recall from my bleary-eyed morning surfing session. The titles and authors followed no standard format, and the Kindle didn't allow me to group them in ways that made common sense. So I couldn't read all of my Iran-related articles before moving on to all of my Tour de France coverage.

That's the big drawback of these devices. They're intended as tools to tame the flow of information, but neither device has put any serious thought into how to channel it, divert it, or create useful reservoirs.

And it's not just for free-content pirates like me who are pumping out PDFs. On the Amazon device, there is no way to look at the table of contents of a magazine before purchasing a single copy, let alone to pay for only the stories you want to read. The assumption seems to be that readers will already know from other sources which articles they want to read are lurking where—call it the print fallacy.

That's a denial of the main mission of journalism: to tell you what's news. On the Kindle—and I know it is very early to complain—all of the signifiers invented over the course of the 20^th century to entice a reader to purchase a single copy of a magazine are absent. There's no cover, let alone cover lines, and no table of contents (though one can migrate through section lists to get to lists of headlines and descriptive decks).

So the Kindle is only halfway toward becoming what a minimally functional reader ought to be. It allows you access to content you know you want but does not allow you to easily discover the content you've yet to become familiar with.

Surprisingly, this is also true of the Kindle store for books. If you know the title or author, you've got a good shot at finding the book you want. But browsing by subject is rudimentary at best, with Kindle offering you the top sellers in well-stocked categories like literary fiction (10,143 titles) and romance (17,043), though it should be pointed out that items 2 and 3 on that best-seller list are different editions of Jane Austen's Pride and Prejudice.

On the far side of the reading experience, after you're done, there isn't a good way to save and store what you've read. It may be sacrilege to say that I don't really miss all the books that used to clutter my house and still pile up by my bedside. But I do miss having a well-ordered and accessible library. I had hoped the Kindle, which brags of storage capacity for 3,500 titles in the DX, would have a way to file and cross-reference my now-portable library so I could still run my finger down the virtual spines of my favorite books every once in a while.

The Kindle does have a useful way to clip articles that are cited in a source. I immediately thought I might finally be able to finish that dissertation I started 20 years ago. But I couldn't find a good way to file and organize those clippings even if I can now export them easily from the device.

These navigation issues are not the fault of the hardware. The Kindle DX's five-way joystick is quick, convenient, and expertly designed. (Plastic Logic's touch screen really isn't markedly better than using Amazon's joy stick, but that's because the touch options are fairly rudimentary.) The problem is the dearth of good places to direct the cursor.

That's a real shame because one thing we've learned over the last two decades in journalism is that information architecture is everything. Charticles, sections, deep captions, multiple points of entry, these are the hallmarks of journalistic innovation—and successful careers—for this generation of editors and readers. But all of that has been thrown out with the E Ink interface. We're back in the days of William Shawn's New Yorker with no table of contents and bylines at the end of the article.

Design limitations don't seem to be a function of the device's constraints. A representative of Amazon told me: "As its core, the Kindle format is based on HTML. We support most features of standard HTML to format and layout text and images on a page."

I'm not really sure what that means, but I can say that when dealing with PDFs of magazine content created within today's design norms, one runs headlong into some serious issues. Neither the Kindle DX nor the Plastic Logic device has what you would think to call a large screen. So a PDF appears at a greatly reduced size. One way around this problem is to turn the device on its side—the PDF is now its normal width or larger—and scroll through the page. Then a funny thing happens. As you page through the PDF—the screen doesn't scroll the way a computer screen does—the page break begins to migrate, making it hard to keep your bearings.

While I was playing with the device, a friend sent me the first chapter of the book he is writing. He decided to use one of those nifty Microsoft Word tools that let him print his chapter as two-page spreads. I'm sure that made him feel more like he'd written a book, but my Kindle had no way to accommodate the format.

Are there ways to surmount these problems? Surely. And I have little doubt that versions 4, 5, and 6 of the Kindle, as well as 1, 2, and 3 of the Plastic Logic device will do that. But if the price remains almost $500—and the Plastic Logic people are not making noises that suggest they plan to compete with the Kindle DX on price—I'm going to put my reading fantasies on hold and stick with the computer.

Photo illustration by Jenny Livengood