Barnes & Noble today discounted its Nook Simple Touch and Nook Color models by $20. The sale, in effect until May 12, turns what were already fine values into some of the best bargains ever for a black-and-white and color e-book reader, respectively.

The Nook Simple Touch will sell for $79 in the sale, down from $99. The Nook Color will cost $149, down from B&N's previous price of $169, which was already lower than the $199 price tag of the device at some other retailers.

By comparison, you'll pay at least $40 more for the devices that most closely resemble these Nooks from Amazon, B&N's arch-competitor. Amazon's Kindle Touch, which competes with the Nook Simple Touch, costs $139 and up (though it's also available in a $99 Special Offers version that includes offers and ads on its screensaver and library). And while the Nook Color was launched as a color e-book reader, it closely resembles the Nook Tablet and Amazon's Kindle Fire tablet, both of which are available for $199 and up—which is $50 more than the sale-priced Nook Color.

As part of the sale, in effect online and in Barnes & Noble stores, B&N is also throwing in a free gift bag for your Nook device, which is usually a $4 purchase.

All these Nooks and Kindles have fared at least respectably in our tests. You'll find the Kindle Touch, Nook Simple Touch, and Nook Color models in the e-book reader Ratings, and the Nook Tablet and Kindle Fire in the tablet Ratings.

Barnes & Noble's new Nook Simple Touch with GlowLight, $139, isn't included in the sale. We are currently completing our tests of that device and expect to post it to the e-book reader Ratings very shortly.