If I've got a manual with the game, I'll read it. That is, as long as the language of the manual doesn't switch halfway through, like in my Dragon Age 2 manual, of which the first few pages are in German and all the others in Polish or something.
Nowadays most manuals are short enough to be read while the game is installing, anyway. Which is actually sad, as manuals always were a great place to find a little bit more backstory, artwork, world building fluff or even just little jokes.