The long awaited Diablo III is expected to be released at the end of this year (Dec 2011) or most probably on January 2012. When it will be released though, you will not be able to buy it immediately due to high demand. Stores will run out of stock and it may take weeks to manage to purchase this incredible game.
Amazon however is offering a pre-order option on their online store. For $59.99 you can pre-order Diablo 3 and you will get it as soon as it is officially released by Blizzard Entertainment. You will have it shipped for Free as well. Another great advantage of Amazon pre-ordering is that if the price of the game changes between now and the release date, you will get the lowest price from Amazon. This means that although the price now shows as $59.99, if Amazon offers a lower price in the future, you will get charged with the lower price.