Races of Destiny is the second book in the series, which started with Races of Stone, and which will be continued by Races of the Wild. This book presents humans, along with half-orcs and half-elves, and also a brand new race, the illumians.
For most players and DMs the chapter on humans, half-elves and half-orcs will not have too much to offer (this is the weak point of the book). However, those who are new to the D&D game, and especially young gamers will find it interesting and useful.
The next chapters offer more for players and DMs alike. The new race, the illumians are really interesting, and I just know that most players will create at least one illumian character to find out the unique versatility of the race.
The chapter on other races is a matter of taste, if you like exotic races, you will like it, if you do not like them, you will find it unuseful.
Prestige classes, new feats and spells are pretty good, and useful. Together with the chapter on illumians, these chapters will be the only ones that older gamers will use.
The chapter on medieval fantasy urbane settings is mostly for new DMs, but it can give new ideas even for veteran DMs. One should never be too old to learn.
Overall, this book is more useful for new gamers, but old gamers will also find interesting things among the pages. It is very difficult to write a fantasy handbook that addresses new and old gamers alike, and this book is a good example of a half-success.