In the same way the Nook is the clearly superior device, the Kindle has the competitive edge in its ecosystem.
Books are easier to find, easier to download, and of course available through a service you already use - Amazon.
But where Amazon really wins in this round is through its Amazon Prime deal, which allows you to "rent" one book a month if you subscribe to Amazon's $75 annual Amazon Prime service (which you should definitely do, like right now).
There are over 145,000 books to choose from - and they're not all crap. It's the kind of feature that can honestly make you feel like you saved money buying a Kindle. Within six months of buying my personal device, I'd "saved" almost the same amount as the Kindle cost.
Book prices are fairly even on both the Kindle and Nook. You can expect to pay $10 for most books. Amazon does allow you to download older books for free while these cost $.99 on Nook, so if you're a fan of classic literature the Kindle might be your first stop.
The Nook Simple Touch with Glowlight costs $139 and comes with everything you could need: a micro-USB cable, a power adapter, and an anti-glare protective screen.
The Nook Simple Touch without Glowlight costs $99, which is still $20 more than the low-end Kindle (which starts at $79). The Nook Simple Touch (without GlowLight) is a much harder sell, as it doesn't come packing that backlighting technology that makes the $139 dollar version such a compelling unit.
Meanwhile, the comparable Kindles are the Kindle Touch - which costs $99, or $139 without "special offers" (which means advertisements), and the Kindle 3G which costs $149 or $189 without special offers.
Neither of the Kindle devices come with wall-chargers and this can feel a bit like you're being cheap-skated. After spending almost $200 could they seriously not throw in the power adapter they charge $14.99 for?