This book was a very pleasant read, and feels very much like classic Bishop Barron. If you follow his media, a lot of this book will feel familiar, but presented at a much higher level. I must admit, when I picked up this book originally, I was looking for some "light" (pun intended) reading, but I was mistaken - the concepts in here are not easy to grasp.
Bishop Barron's introduction explains the book's purpose as evangelistic, and that his intended audience is for searchers, not necessarily for those already bought in. I think the book is still definitely useful for those who are bought in (and perhaps more so), as it provides an articulation of many of Catholicism's difficult concepts for an evangelist to utilize.
One criticism that I have often heard of Bishop Barron's work is that people have trouble understanding it, or it is too esoteric or big-word-y for them. Bishop Barron, in the introduction, is aware of this and makes no apologies, explaining that the alternative is to dumb things down, a move which, he argues, is done all too often and which is at least partially responsible for the mass reduction in credibility of the faith. He writes for an intelligent reader, and at least at the college level. He is even cheeky about it at points (e.g. "by this I simply mean the ontologically evanescent quality of..."). Nonetheless, he provides all of the background information that you need to know. A beginner can read this book and benefit from it, but only if he wants to - you won't understand this book if you're not committed to understanding it. Therefore, I wouldn't necessarily recommend it for your teenage nephew who is skipping church because he thinks it's uncool, but I would recommend it for someone who is earnestly exploring and is committed to getting to the bottom of what it is that we call God. This would also be good for someone who is early-conversion, in the middle of or just finished RCIA, or anyone who likes talking to the disaffiliated or the loosely-affiliated about the faith.