I enjoy games that have replay value. Like you said, it's rather boring just replaying a game or re-reading book that is just the same. Knowing that there may be half of the content I missed because I was exploring and engrossed in something over there sounds great. If I play the game for 90 hours to see everything in a single playthrough or play for 90 hours in two playthroughs, I'm still spending the same amount of time and I've seen everything. Plus, some of the things probably will have greater context on a second play.