Online retailer Amazon.com Inc. said Thursday it is introducing a new version of its higher-end Kindle at a lower price as competition among electronic-book readers intensifies.

The new version of its Kindle DX has a better screen that will display sharper images.

The large-screen reader, which Amazon hoped would catch on as a textbook substitute at universities, has free wireless over 3G cellular networks. It will be sold for $379, about 23 percent less than the $489 Amazon charged for the previous generation of the larger Kindle DX.

Amazon also said it improved the way the Kindle DX handles PDF documents, potentially solving a major complaint among students who tested out the Kindle in a pilot program over the past academic year. The original Kindle DX didn’t allow people to zoom in closer on PDFs, leaving graphics and small print difficult to decipher.

The new device can be pre-ordered immediately and will ship on July 7.

Could a blind person drive a car? Researchers are trying to make that far-fetched notion a reality.

The National Federation of the Blind and Virginia Tech plan to demonstrate a prototype vehicle next year equipped with technology that helps a blind person drive a car independently.

The technology, called “nonvisual interfaces,” uses sensors to let a blind driver maneuver a car based on information transmitted to him about his surroundings: whether another car or object is nearby, in front of him or in a neighboring lane.