I have taken to bringing a book as well, not so much to stay awake, but to help me SIT STILL (that's something Ive gotta keep working on). The place I hunt whitetail is mixed oak woods, covered with leaves in hunting season (unless it snows). I know deer can be quiet, but I ALWAYS hear them before I see them. So far.... I'll be sure to tell you when I see one first!
. Yes I do scan constantly with eyes and binos, but still, my experience is hearing them first.
As for falling asleep, it's a problem I have. I take solace in the fact that I am never drowsy during peak times (first few hours before and after daylight and last couple of hours). Just not a problem because of anticipation. But mid day, especially after I eat my lunch. Well I might as well get out of the stand and walk around to kick something up for the others, or still hunt because if I sit there, I'll nod off for sure. I always make sure I'm safe and if not, I'll go down and just take a nap at the base of the tree to get it over with. I'm a "power nap" guy and 5-30 minutes nap will be like a shot of adrenaline for me.
But what the other guys have said, hunting is a bunch of different great things - and one of them is a peaceful light doze in the fresh air and quiet of the woods. Nothing like it and worth losing 30 minutes at mid day, if you ask me.