I wish I had read something like Racing Towards Excellence when I was much younger. Instead of getting the inside story on a number of things I just didn't know, I had to learn from my own mistakes. I highly recommend the book to anyone in their 20s or younger.
The authors discuss a number of topics geared towards increasing the happiness of the reader. Some of their views are rather contrarian and not in line with the conventional wisdom, and this is where the book is the most useful in my opinion. Generally, a young person will not know whether the conventional wisdom is right or wrong, or they may have an inkling that the conventional wisdom is questionable, but don't have the confidence to go against it because they know so little.
But because the book covers so many topics, it really doesn't go into a lot of depth into any one. For someone who has already read a lot about some of these topics, the book is likely not that useful, which is why I wouldn't recommend it to people who already read.
The authors also have perhaps a little too much confidence in their assertions. They don't leave a lot of room for uncertainty with respect to certain topics, even though I've read enough on the subjects to know that they should have. In one particularly glaring example (keeping in mind that the book was published in 2009), the authors talk about how Tiger Woods uses virtuous circles that propel him as part of a "balanced family life", which obviously turned out not to be the case.
I think the authors also sound very authoritative on some subjects, but for which they don't provide empirical backing. But if you accept the contents of the book as the opinions of two very talented people rather than as fact, I think you can easily accept the book as far as it goes.