This book was given to my Grandfather in Law when he was confirmed into the Catholic Church. My Grandmother-in-Law gave it to me on Thanksgiving, because she thought I would really like to read it, and I thoroughly enjoyed it. I wanted to discuss it briefly because it was an excellent book, and well worth reading, to both Catholics and non-Catholics. If you click on the title of this post, it should take you to Amazon, where you can buy a used copy of this book for 1 penny! Thankfully she gave it to me, because it is out of print and I don't think I would have found it anywhere else.
First, we need to note that this book was originally written pre-Vatican II. That being said, we need to realize that a lot of its language reflects the Church's relationship with Protestants before that council, a very different relationship indeed. If any of you have read books from the 50s and 60s, you will quickly recognize the tone and type of language that Father O'Brien uses. It can seem very harsh at times, and I think he assumes that everyone will logically come to the same conclusions that he does, perhaps not realizing that people's own inherent spiritual tradition and biases can cause them to come to different conclusions altogether.
That being said, I think this book is very clearly and easily written. It gives some insights into Catholic teaching and Tradition that almost no other book I have read can do so clearly. I imagine that it was probably read by young faith groups or in RCIA classes in the past, because it really is nice to do an overview of Catholic teaching, but also gets into issues like an entire Chapter on St. Joseph that many other cathechetical books do not do. His teaching on marriage and sexuality is very well done as well.
If you are a member of my former denomination the "Church of Christ" (and I know there are several who are and read this blog), I highly recommend this book because the style and prose are highly reminiscent of many books that are read by those there. The way it is laid out reminded me of many books that CoC writers used to write, only here you will see that the same "plain logic" that they lay out can be understood very differently by Catholic thinking. It also answers a lot of questions that you guys have posed to me here and elsewhere.
If you do pick up a copy of this book, try not to get too upset at the harsh language he uses towards Protestants at times. I think he wrote it from a loving perspective, but I can see how it could be a big turnoff to someone who really rejects the Catholic Church. It was updated after Vatican II, but mostly that update only takes place in the last Chapter where he really hits on the idea of ecumenicalism.
I give it a 9/10 - only because it is in need of a more thorough updating. As for explaining the teaching of the Church and such, it is perfect for both Catholics and non-Catholics, mostly because it does not get bogged down in too much theological teaching, while at the same time being advanced enough to explain complex teachings.