Kindle Unlimited is Amazon's subscription ebook service. It usually costs $10 a month for access to a catalog of around 750,000 ebooks (and a few audiobooks). But under the new bundle program you can get the basic Kindle with 6 months KU for $99, or about $40 less than what it would cost separately ($79 + 6*10 = $139).
Amazon is also offering similar bundles for Fire HD 6, Kindle Paperwhite, and the Fire HD 7.
The bundle offer is only good for these 4 devices, so you can't buy a Voyage or a Fire HDX and get the 6 months free, alas. But on the upside I've checked and I can confirm that you can buy a bundle as a gift. And like Amazon's past bundle deals, the discount is applied when you check out.
So far as I know this is the first time Amazon has offered a bundle for KU. Their smaller competitor Oyster has worked with QVC to bundle its service with select tablets, and as you might recall Amazonwhich combined Amazon prime and Amazon hardware.
Are you going to get one? What about giving one as a gift?