I remember when I was younger, when my video game purchases were limited by my allowance and thus primarily for my Gameboy or classics for my PSX and very infrequent, one of the very best things about making the purchase was reading the manual on the car ride back home. Man did I ever love reading the manual. There is the sense of studying it closely so that when I played the game, I would be prepared to operate its controls, but mainly, the manual was my first leap into the game's world. Most manuals are simply guides to the controls, but almost all of them have at least some little blurb about the environment. Some manuals even had more information about the game world than the game itself (cf. the Marathon manuals). Often, manuals gave you your first explanation of how the game world worked, which is always important for me as it is my first step for immersion. I also remember what a treasure trove finding all the old manuals for my grandmother's NES games. That was pretty awesome.
There was always something interesting in the manual for me, little previews to get me psyched up even more than I already was. And seeing as I had to save up sometimes for months in advance in order to buy a game, I was already pretty psyched up. Then, as now, I only bought games I really, really wanted for sure, which were few and far in between.
Reading the manual now is a much different story. I buy games a lot more often now that I have disposable income, and since I am usually driving myself, I usually can't read the manual on my way home unless I want to get into a car accident. But the manual is still the first thing I look at when I get home, and reading it is the first thing I do, before I ever play the game.
These days, I frequently find myself disappointed by manuals, sometimes to the point of absurdity. Dragon Age: Origins is a fantastic game with a terrible manual. I can't even remember what it said, except that it made no sense to me whatsoever and was pretty disorganized and all around hard to read. I'm sure there was some valuable information in there somewhere, but I couldn't tell you what, and this is the pattern I see most often these days. It seems manual writing is a bit of a lost art. I don't know if game publishers have a philosophy for manuals, and the lack thereof may be the reason why they are so wildly different from game to game. It would be nice if a manual made me excited to read on about when to press A, but I also have to recognize that the manual, as an auxiliary piece of literature which is often made redundant by in-game tutorials, is not necessarily important enough to spend a lot of time or QA on.