For those with an interest in the history of the earliest Christians, this books is an awesome and enlighting read. It starts with the Didache, a writing that is contemporary to the New Testament and covers the first four hundred years of Christianity. If you want to know what to believe, then a logical person to ask (if you could) would be the people who were contemporaries of the apostles or who came immediately after. Well, we can't ask, but we can read what they wrote, which is the next best thing.
Jurgen's The Faith of the Early Fathers is a particularly useful collection of those writings. It is arranged first by authors, which is nice for those who want to study the writings of one early father at a time. Better, though, for the rest of us busy people is the doctrinal index. Each issue of doctrine (from the Bible, to the papacy, to Mary, etc.) has a section, and within that section it is broken down into specific points of doctrine, then each of the points has a paragraph number(s) showing where you can read what these early fathers wrote about that issue. So, when you need to, you can lay your hands on what (for examply) St. Justin Martyr wrote about the Eucharist in about one minute flat, without having to spend hours reading and searching his writings.
The Faith of the Early Fathers is the easiest to use compendium of early Christian writings I have ever seen. Anyone who gets this book is going to be just thrilled with what they can quickly and painlessly learn with this reference in their hands.