Your high school English teacher may have told you that the value of a good book was immeasurable, but Walmart and Amazon have a feeling that it hovers somewhere under 10 bucks. The two online giants have begun a deep-discount war that is more reminiscent of neighboring delis with erasable sandwich boards than retail behemoths.

Walmart fired the opening salvo on Thursday with a promotion offering their top 10 pre-ordered books (including Sarah Palin’s memoir and new books from Stephen King, James Patterson, John Grisham, and Michael Crichton) for only a sawbuck — including free shipping. Amazon responded to the broadside by matching their price, but as of this morning, both deals had slipped down another notch to a staggering $9 per popular new hardcover. That’s over two-thirds off the cover price of Palin’s Going Rogue, which, according to the Wall Street Journal, retailers are hoping will provide a shot in the arm for somewhat sluggish book sales this fall.

While this might seem like just some good old American capitalism at work, it’s also a cause for reflection. These are two of the largest outlets for book sales in the world, and although it might spell better deals for us, the consumers, it’s hardly an auspicious sign for the vitality of the industry. It’s even worse news for independent booksellers who aren’t able to compete at anything near the level of Sam Walton’s little corner store. But maybe the most interesting aspect of this is its implications for physical books themselves. Amazon’s pricing for these hardcovers is now lower than the $9.99 tag on most Kindle editions. Is this a sign that e-books are starting to have a depreciative effect on the genuine article? The inevitable might have just inched a little bit closer.

What do you think? Are you happy for the change in your pocket, or are you worried for the change in the market?