At a Thursday, September 6, event, online retailer Amazon unveiled four Kindle Fire tablets - two of which comprise a much improved Kindle Fire HD lineup - as well as a new Kindle e-reader.

One of the new Kindle Fire HD tablets is a 4G LTE-enabled device, boasting an 8.9-inch screen and 32GB storage capacity. The tablet will directly challenge the Apple's new iPad; especially since its $599 price-tag will be notably lower than the $729-priced 9.7-inch, 32GB iPad with 4G capability.

Though the 8.9-inch Kindle Fire HD will not be shipped before November 20, Amazon will start shipping a smaller version in the newly-announced HD line - the 7-inch Kindle Fire HD - by September 14.

According to an Associated Press report, the new Kindle Fire HD line will have a much more vibrant display than the original Fire tablet, thereby underscoring an added appeal for the users to purchase movies and TV shows for watching them on the device.

Meanwhile, other than introducing new tablets, Amazon also unveiled a new light-up Kindle Paperwhite e-ink reader at the Thursday event. The new, fifth-generation Kindle e-reader boasts a "front-lit" touch display and 62 percent more pixels, with its contrast being 25 percent more than that of the previous models.

To be shipped by October 1, the Kindle Paperwhite will be available in two versions: a Wi-Fi-only e-reader; and a `Wi-Fi plus 3G cellular' version. The models will cost $119 and $179 respectively with Amazon's "special offers"; and $139 and $199 without the offers.