I won't try to summarize so many witty and similar quotes from great men who tell us, if we truly research what the early church looked like and sounded like, we would find it hard to be protestant.
But this book is a great, concise way to sample a pile of early christian writings without gathering them yourself.
For a Catholic, this book will confirm your faith and give you info with which to defend against critics.
For non-Catholics... I'll just speak for myself and say, I had to really sit down and consider if I had the stubbornness to cling to various doctrines, when men who learned from the apostles themselves (first century believers) thought otherwise. Do I, or one of my pastors living in 2013, really know what scripture means better than a guy who was led to Jesus by the Apostle John?