Amazon isn't having any trouble selling its Fire TV set-top box. Immediately after launch, it quickly rose up to become the company's best selling electronics item and hasn't dropped since. Fire TV even managed to dethrone Google's $35 Chromecast, proof that it's off to a rousing start. But Amazon wants even more people to buy it, so the online retailer is offering select customers a free 30-day trial of the streaming box.

The promotion is invite only, and it's not exactly clear how Amazon is picking the lucky participants. But if you receive the above email, all it takes is hitting the "apply offer" button and a Fire TV will be added to your cart — and you won't have to pay for it. At least not right away. (Amazon also covers shipping costs.)

You do need to provide payment information to take advantage of the offer, however. If you still have the Fire TV after 30 days, Amazon will assume you want to keep it forever and you'll be charged the regular $99 price. But if you decide the company's set-top box isn't for you, return shipping is also handled by Amazon. It's hard to beat that deal.