Dishonored was just released today. However, it’s not too late to pick it up for a good price at Green Man Gaming (GMG). Use the 25% off voucher code GMG25-EVFWS-4Z4ZN (expires on Oct 12th), which makes the game $45.00.
Dishonored uses Steamworks, so Steam activation is required.
The reviews have been very positive for this game so far.