Amazon.com (Nasdaq: AMZN) is giving its e-book reader another feverish marketing push. Now that the company's supply-channel woes have been licked, it's devoting a good chunk of its landing page to swaying buyers into purchasing the $399 gadget.

The leading online retailer is devoting the heart of its homepage this week to a promotional note from CEO Jeff Bezos. A snapshot of boxed Kindles on pallets in the Amazon warehouse accompanies the note, perhaps to appease the Doubting Thomas in the crowd who needs to see it to believe it.

The note then links to Bezos' annual letter to shareholders, where the Amazon chieftain spends the entirety of the annual report's opening salvo pimping the Kindle.

I can't blame Bezos for rallying around the Kindle. It is a potential game changer. If it takes off, Amazon has a meal ticket to cash in as the gateway to literary digital distribution. It can become to books what Apple (Nasdaq: AAPL) has become to music -- a savior riding in on the promise of inventory-free media delivery.

Unfortunately, few know how close Kindle may be to reshaping the industry, because Amazon has been so tight-lipped about how briskly the device has been selling.

Show me the money
Bezos loves to talk numbers when it comes to the Kindle. Unfortunately, those numbers tell us nothing about the actual success of the device.

The first batch sold out in 5 1/2 hours? That addresses the initial supply shortage, a problem that plagued the device during the critical holiday shopping season.

There are now more than 110,000 titles available? That's great, but how about an actual sale number of those titles? Investors would feel cheated if Apple didn't update its shareholders on the iPod and iTunes milestones, and Apple is a company that keeps secrets close to its vest.

There are more than 2,000 customer reviews on Amazon? Great, but that, too, tells us very little. You don't have to buy a Kindle to post a review. That's obvious once you begin going through some of the posting.

"I would love to buy one but at $400, I can't talk myself into buying it," one reviewer writes.

"I am writing this less as a review than as a request," begins another.

Why is Amazon allowing non-owners to post reviews? It's not as if this is a product one can buy anywhere else, save for the occasional third-party auction sale.

I may have taken shots at travel site Orbitz Worldwide (NYSE: OWW) over the years, but I'll give it credit for letting only bookers confirmed through its site provide travel reviews. If not, you open yourself up like rival Expedia's (Nasdaq: EXPE) Trip Advisor has to self-serving reviews or scathing critiques from rivals.

Perhaps more telling is that less than half of the Kindle reviewers have given the device Amazon's highest five-star rating. If these are the early adopters who didn't flinch at the $400 price tag, the reviews won't get much better until Amazon either improves the features or lowers the price.

Mum's the word
Amazon isn't shy about its sales figures. It's quick to rattle off unit data on Dec. 26. It has even attached continually updated meters to high-profile items such as Scholastic's (Nasdaq: SCHL) Harry Potter books or overall holiday sales with its Delight-o-meter.

There is no reason it shouldn't attach a meter to its own Kindles. Maybe it's embarrassed to show too low a number. Because the Kindle is now readily available, Amazon has presumably filled the backorders that accumulated over the past five months.

So what? Is Amazon afraid a low number will frighten away potential buyers or fence-straddling publishers? I think a low number may help Amazon's cause, because it encourages buyers to hop on the early-adopter bandwagon. Can it hurt? Since the Kindle's mid-November debut, Amazon has been actively promoting its Kindle with apparently little success worth bragging about. Maybe it's time for a new tack.

Whip out the meter, Amazon. Digital delivery is too important for your future -- in movies, music, and now books -- to be shy about it.

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Longtime Fool contributor Rick Munarriz has been shopping online for about as long as Amazon.com has been in business. He does not own shares in any companies in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.