Barnes & Noble (s bks)'s two new Android (s GOOG) Wi-Fi tablets, the 7-inch Nook HD and 9-inch Nook HD+, aim to compete with other moderately priced tablets such as Amazon's Kindle Fire(s amzn) and Google's Nexus 7. But the new Nook tablets, starting at $199 and available in October, differentiate themselves most from competitors when it comes to some new reading and discoverability features.
