Valve and Prima have announced that Prima guides are now available in steam. The guides appear in-game through the Steam's UI overlay functionality meaning you don't have to quit the game or Alt-Tab to read them.

Currently available are guides for Dragon Age: Origins, Just Cause 2, Left 4 Dead 2 and Battlefield: Bad Company 2 with more on the way.

To celebrate, Steam are offering 50% off on all Guides.