That isn't always the case. Too often, people get book deals just because they're famous. No one seems to care if they can write., or if they have anything to say. The work is usually farmed out to ghostwriters anyway, which makes it ironic when they can't write either. There's no pressure to make a good book; the publisher is selling the famous name, not the book. The only loser is the reader. I blame Al Gore.
Sorry. I didn't mean that to turn into a rant.
What I meant to say was that Keller writes well. Many books of the kind first try to bury the reader in statistics or drown him in syrupy sentimentality before bringing in bibical reasons to care. Keller disdains tactics like that,keeping a close focus on Scriptrure the whole time.
Why should we care about the poor? Keller gives us a biblical answer, and shows how that answer can look played out in the world. This book's goal isn't to make you feel guilty, but to help you act biblically, and I recommend it.