GOG often has a sale or two going on at any one time, and this newest one includes games like Tropico 5, Antihero, and Banner Saga, all for discounted prices, up until the sale's end on September 19.
This all sounds normal, but there's an added bonus, as spending over certain amounts ($15 USD, which is around £11.29), will get you three free games, these being Tropico Reloaded, Breach & Clear: Deadline Rebirth, and Kyn. Will this convince you to shell out on some of the games in the sale?