Overstock.com Inc. today announced that it has dropped the prices of books on its e-commerce site so that they are 10% lower than Amazon.com’s prices, as of July 22.

The promotion applies to the roughly 360,000 titles sold on both Overstock.com and Amazon.com, Overstock says.

The promotion highlights Overstock’s inventory of more than 466,000 books, says a spokesman for the retailer, which is No. 31 in 2013 Top 500 Guide.  “Everyone is accustomed to looking at Amazon when they’re shopping for books,” he says. “We’re hoping this will get them to look at Overstock first.”

Overstock says it will examine consumers’ response to the promotion before it sets an end date. 

Overstock executives already claim they offer cheaper prices than Amazon on most products. Patrick Byrne, the e-retailer’s chairman and CEO, said last week that Overstock.com is on average 9% cheaper than Amazon on products that both e-commerce sites offer.

While Amazon.com, No. 1 in the Top 500 Guide, launched as an online book retailer, its focus has largely shifted away from the sale of physical books, thanks to the success of its Kindle e-reader, and its move into other verticals, such as high-end fashion and “cloud” or Internet-based computing and data storage services via its Amazon Web Services division. The retailer in 2011 announced that its sales of digital books for its Kindle e-reader outpaced printed volumes.

Amazon.com could not be reached for comment.