Once again, Overstock.com (NASDAQ:OSTK) is trying to give Amazon.com (NASDAQ:AMZN) a run for its money -- and offering to help customers save a bit of money in the process.

Last month, Overstock announced a plan to sell books offered on Amazon for prices at least 10% below the prices Amazon was charging, telling shoppers in the promotional material that, "If you're going to buy a book this week, you're crazy not to shop Overstock.com first. And if you weren't going to buy a book this week, you should reconsider."

On Monday, Overstock tweaked that plan a bit. According to Overstock's latest announcement, the Internet retailer is going to match Amazon's prices on any book it sells and offer its own "Club O" loyalty club members a 15% credit on any book's sales price, to be applied against future purchases on Overstock.com. Overstock charges $19.95 per year for Club O membership.

Overstock CEO Patrick Byrne noted in a statement: "Last month we started a book pricing war with Amazon. We're hoping to continue that battle, in a way that lessens any harm to the mom-and-pop booksellers we consider our comrades in arms."

Overstock clarified that by only matching Amazon's prices, and offering further discounts, it's intention is not to add to pricing pressure on small, bricks-and-mortar retailers, but rather to simply steal online sales -- that wouldn't have gone to the mom-and-pop stores in any case -- away from Amazon.