This article compares the Barnes & Noble nook with the newest Amazon Kindle 3G. If you want to compare the nook with other Kindle versions, please see Kindle DX vs nook and Kindle (original) vs. nook.
If you are in the market for a good color e-reader with low glare display, good physical design, better personalization choices and more user accessible storage, then Nook Tablet is a better choice. But if you are looking for a color e-reader with simplified buying or renting books and media feature from Amazon's ecosystem, better web browsing and navigation capabilities, then Amazon Fire is better suited for your needs. 
edit Display and User Interface comparison
Both Kindle 2 and nook have a 6-inch display with E-Ink technology, 16-level grayscale contrast and adjustable text size. However, the display of the nook is less responsive than the Kindle's. David Pogue at the New York Times writes that
Even though it’s exactly the same E Ink technology that the Kindle and Sony Readers use, the Nook’s screen is achingly slower than the Kindle’s. It takes nearly three seconds to turn a page — three times longer than the Kindle — which is really disruptive if you’re in midsentence.
The Nook also has a 3.5-inch color touch screen that is used for highlighting text, adding bookmarks and navigating the internal library. The touch screen can be turned into a keyboard for making annotations and taking notes, or a controller for the MP3 player. Arrow keys on either side of the device control page-turning. When not in use, the nook's touch screen goes dark.
While the color touch screen appears to be a solid plus for the nook, David Pogue writes that
That “color touch screen,” for example, is actually just a horizontal strip beneath the regular Kindle-style gray screen. (In effect, it replaces the Kindle’s clicky thumb keyboard.) This screen is exclusively for navigation and controls. Sometimes it makes sense; when you’re viewing inch-tall book covers, for example, you can tap to open one. At other times, the color strip feels completely, awkwardly disconnected from what it’s supposed to control on the big screen above. Worse, the touch screen is balky and nonresponsive...
edit Available Content for the nook and the Kindle
According to Amazon, the Kindle has access to more than 360,000 e-books as well as newspapers, magazines and blogs that can be wirelessly downloaded from Amazon.com. According to Barnes & Noble, more than one million newspaper, magazine and e-book titles can be purchased online at BN.com for the nook. This includes access to over 500,000 free e-books. These e-books are also available on the Kindle but Amazon does not count them when they advertise because they are copyright-free, low-resolution scans available on Google Books.
According to David Pogue,
Of the current 175 New York Times best sellers, 12 of them aren’t available for Kindle; 21 are unavailable for the Nook. Kindle books are less expensive, too. Inkmesh.com studied the top-selling 11,604 books for early November, and found that 74 percent of the time, Amazon offers the lowest-priced e-books (cheaper than B&N or Sony) by an average of 15 percent.
edit Wireless Connectivity
The Kindle 2 3G uses Sprint's network to connect to Amazon.com to download content. The nook uses AT&T's network for the same purpose. The nook also offers 802.11b/g Wi-Fi connectivity to get online, plus a free Wi-Fi connection in all Barnes & Noble stores. However, you get no notification when you are near a wireless hot spot. And if the wireless network requires a login or welcome screen, you cannot log on to it.
The nook's LendMe feature allows e-books to be shared for 14 days. The borrower will need Barnes & Noble’s free e-reader app, which is compatible with PC or Mac computers as well as BlackBerrys, the iPhone and the iPod Touch. As with a paper book, you cannot read your e-book while it’s on loan. The other drawback of this feature is that each book can only be lent once - ever. Not all books can be lent either. You can lend a book only if its publisher has allowed this feature. And so far, B&N says, only half of its books are available for lending — only one-third of the current best sellers.
Amazon.com does not offer this feature with Kindle.
The Kindle offers an experimental text-to-speech feature exists, but the computer-generated voice is stilted. The Kindle also supports audio books.
Both devices have speakers and a headphone jack for listening to MP3s.
edit Cross-platform compatibility
The Kindle relies on Amazon’s proprietary file format so it is not compatible with titles purchased from other e-bookstores. But Amazon offers a free application that allows its books to be read on an iPhone, a PC or a Mac. Amazon also remembers where you left off if you change devices.
The nook offers the ability to download and read PDF files, which can be used to read e-books in PDF format. While the nook does not support Microsoft Word, the Kindle does.
edit Reliability and Performance comparison
David Pogue writing for the New York Times in December 2009 wrote that
the Nook may have some hardware advantages — a removable battery, a memory-card slot and (because of narrower plastic margins) a slightly trimmer shape — but the Kindle is still a better machine. It’s faster, thinner, lighter and much easier to figure out.
He also found the Kindle's software to be faster, more user-friendly and less confusing than the nook.
edit Battery Life
The Kindle has a battery life of 30 days (with wireless off) whereas the nook can be used for 10 days without recharging.
Dependent on the features, storage and technology, Kindle can cost anywhere between $79-$379 (Kindle $79,Kindle Touch $99, Kindle Touch 3G $149, Kindle Keyboard 3G $139, Kindle DX $379, Kindle Fire $199). Nook is available from $99-$249 (Nook Simple Touch $99,Nook Simple Touch with GLowlight $139, Nook Color $199, Nook Tablet 8GB $199, Nook Tablet 16GB $249).
- Kindle Wireless Reading Device (on Amazon)
- Kindle DX Wireless Reading Device (on Amazon)