When the Barnes & Noble Nook e-book reader was announced last week, I wrote about the company's strategy to beat out Amazon's Kindle by making B&N e-books available on many different devices, giving customers more places to buy and read their books. It only took a couple of days before Amazon followed suit and announced it too was making a Kindle app for PCs. Versions for Mac and BlackBerry are supposedly in the works.

Choice is good. But Marion Maneker over at The Big Money argues that while the Kindle helps Amazon's business, if the Nook turns out to be a big hit it could wind up hurting Barnes & Noble. As book prices fall due to heavy discounting, it is becoming harder for the bookseller to support its expensive stores and many employees. The Nook may make the problem worse by robbing sales from the company's physical bookstores while setting an expectation among its customers for cheaper books.

Maneker writes:

"Amazon has established the idea of $9.99 e-books, especially for best-sellers ... On the most heavily trafficked titles, BN.com will have to spend money to keep up the $9.99 price point. But Amazon has mountains of cash from its other businesses to support this; B&N does not. The physical stores don’t generate enough profit for that. Meanwhile, those stores are getting beat up by Wal-Mart, Target, and Amazon, as they establish a $9 price for the biggest best-selling titles."

It will be interesting to see how B&N tries to get around this. Does it shutter many of its physical stores and move more toward becoming an online and e-book seller? Or does it find a way to use its physical bookstores to offer customers an "experience" that online stores can't?