I also gave this book up fairly quickly? This is because it is filled with surveys showing why Catholics and most Christians are happier and more likely to be successful people with more friends, etc. Surveys have shown that people who go to church are more likely to be happier and live longer lives than others. There is also evidence that prayer is powerful. However, I couldn't help feeling that Donahue chose the surveys which supported his thesis!
Reading about all these studies was rather tedious. However, I recommend dipping into this book whenever you need to feel better about being Catholic!