What to do....

I know it has been discussed before but o-well...What does a pilot do when doing a flight that is over 7 hours...I believe for some airlines 8 hours requires 3 pilots...but whatever that amount is what is there to do at FL390 cruizing across the altantic at mach .843?..I was listening to ATC chatter over some Ocenaic clearence and once in a while you would here a bunch of pilots talking as they were crossing and awaiting their clearance but other than that little was heard. Do they read books....which would get long after 3-4 hours, atleast for me...?