Emily already reviewed this book, and wrote a great summary and introduction here, which I am not going to try to replicate. I really can't improve on Emily's review so I am just going to rant inanely about how the book made me feel.
I discovered that I really don't like reading about how I should live my life differently. I get it, my priorities are less than ideal. I am not going to change my life to one of service, I am not going to go teach in Africa, I am probably not even to forgo buying the designer handbags so despised by Kristof and WuDunn. I don't care what the context, position, or arguments are: anything trying to get me to do anything will be met with resistance. This book was really raised my defenses.
Don't get me wrong, I was profoundly disturbed by the anecdotes and statistics. It makes me grateful to be a middle class American, and really angry about all the crap that people do to each other. I am not averse to supporting these causes, but to be honest I will probably keep donating to and volunteering with my favorite animal shelter because it's more rewarding. Maybe I just can't face rape victims and whatnot in a personal way.
More about the profoundly disturbing stories. Reading some parts of this book literally induced panic in my brain. It is really horrifying. The stories that Kristof and WuDunn go into are just too awful for words. I am sure I am not going to be forgetting images from this book any time soon. This is not a book for kids. It's all true stuff, and at some level I suppose it's important for everyone to be aware of their world, but I would not suggest this book to a sensitive person or a child.
In summary, if you want to be motivated to hate people and maybe donate some money (and you think you are more amenable to such suggestions than I am...) you might enjoy this book. If you just don't like being told what to do, read something else!