I'm about 100 pages into it, but it's already clear that (1) Tiger works hard at the game of golf and (2) he loves the game. Here's what he says on page 85 of the book:
"I love to practice. In the summertime, it's "have light, will play " -- sometimes as much as 14 hours. There's always stuff to work on. You never, ever arrive, but it sure is fun trying. To me, work is fun."
Now, I was never as good at basketball as Tiger is at golf, but I know how he feels. During the summer, as a kid (and all the way through college), I'd play basketball from sunup until sundown. [Many days I'd play at the La Jolla Rec Center, not far from where Tiger's playing the U.S. Open this week.]