The Kindle isn't a device- it's a book. Its functions are limited to choosing something to read, displaying text, and turning pages, and that's exactly what I want. I love the fact that I can't check my email, facebook-stalk, or waste time on hundreds of pithy, short-form Google Reader feeds.
There is no mail client, no apps, no crashes, no running out of battery (it lasts weeks on a charge). With the awkward keyboard of the previous generation gone, it weighs next to nothing, reads one-handed for hours on end, and easily fits in a coat pocket. You can loan books to friends or check them out of the library, too.
Buy this for your mom. The screen looks and reads like real paper, there's no learning curve to use it, and it fits in a purse better than most paperbacks. Buy it for your kid- it's half the price of a videogame console or iPod touch, and they'll spend their time reading instead of playing Angry Birds. Buy it for your grandparents- there are no fancy bells or whistles to freak them out, and they'll love the high-contrast print and adjustable text size.
Get the Kindle for $79 on Amazon.com- I can't think of a better holiday gift. The $79 includes "sponsored" screensaver ads than run only when you're not reading, but if that irks you, spend the extra $30 on the ad-free version. Skip the more-expensive Kindle Touch- you won't use the web browser much, 3G is limited to downloading books and browsing Wikipedia, and you don't want to get fingerprints on the screen. The Fire is interesting, but it's a tablet, not a book.
E-ink. Note the perfect readability even at off-center viewing angles. Cuts glare pretty well, too.
Reading on an iPad vs. a Kindle.
iPad vs. Kindle size comparison. The kindle weighs about a third as much, and is easy to hold in one hand.