Amazon.com will introduce two new versions of the Kindle e-reader on Thursday, one for $139, the lowest price yet for the device.

Amazon is hoping to convince even casual readers that they need a digital reading device. By firing another shot in an e-reader price war leading up to the year-end holiday shopping season, the e-commerce giant turned consumer electronics manufacturer is also signaling it intends to do battle with Apple and its iPad as well as the other makers of e-readers like Sony and Barnes & Noble.