Steam users can now request and receive a refund for any reason, providing it’s been less than 14 days since the customer made the purchase but only if they spent less than two hours in the game.
According to the updated refund policy, a full refund will be offered on the game as well as any DLC or pre-purchased items as long as the core game wasn’t player for over the two hours mark. However, some forms of DLC are listed as a non-refundable purchase, so users will need to keep that in mind when clicking the buy button.
Refunds will be credited within a week to either to the user’s Steam Wallet or payment method used when making the purchase.
Gifts cannot be refunded once redeemed, the same goes for movies and those banned by the Anti-Cheat system.
Valve states that it will stop handing refunds to those which abuse the system, but it does not “consider it abuse to request a refund on a title that was purchased just before a sale and then immediately re-buying that title for the sale price.”
More information is available through the link, and you should give a thorough read.