It tells us all about his life, not just as a teenager as we see him in the movie, but as an adult as well, who gets married and becomes a father. But the most important thing is that it shows us how Bruce Springsteen appeals to everyone, no matter what colour, religion or nationality. And it shows us how his music can help people through hard times, even if they're not the "typical" American fan.
Having lived in Britain myself, during most of the period that the main events in the book take place, and having socialized with members of the British Asian community while I was there, many of the things and events described in the book are familiar to me.
If you're Bruce fans you have probably already seen the movie, but I strongly urge you to read the book as well.