Most likely, if you have ever read the world's best selling book, the Bible, you have read something at some point in the Bible that made you think, "I wonder what that means." Perhaps, as you've read through the pages of the New Testament, you've noticed that many times, the author of a particular book, whether it was Matthew, Mark, Luke, John, Paul, Peter, etc, would quote from the Old Testament and you wondered if that quote fits with what the original author was trying to say. Old Testament quotations found in the New Testament are in abundance. Many of those quotations make perfect sense. They don't really cause the reader to pause and wonder why the New Testament author chose to quote a particular Old Testament reference. But, there are a fair number of places in the New Testament where there is a quote from the Old Testament that, if you go back to the Old Testament passage (from where the quote came from) and read that passage, you'll be left to wonder if the author of that Old Testament passage was truly referring to the issue that the New Testament author seems to be addresssing. This is the topic of "The Old In the New" and this topic must be addressed for any person who wants to be an excellent student in understanding the pages of Scripture. It's not a trivial matter to handle God's Word carelessly. We must demand of ourselves that we are faithful to the text and what the author meant by what he wrote. In fact, Scripture says that man of God is approved by God when he handles accurately the word of truth (2 Timothy 2:15).
I have come to have a deep appreciation for Michael Vlach as an author (See his book, "He Will Reign Forever"). He writes in a humble and gentle manner and, even if one were to disagree with him, you couldn't accuse him of being rude or arrogant. In this book in particular, Vlach presents five main approaches to understanding how the New Testament authors used quotes from the Old Testament. In explaining the five different approaches, he presents his own view/approach (from those five) and then walks the reader through all of the various passages where a New Testament author quotes the Old Testament, demonstrating the problems with each of the other four approaches/views and then gives a reason for his view, his approach. Vlach is gracious in his writing and he is likewise compelling. Because of this, I believe he will get an audience from those who, either have another approach, or, those who are ignorant to the issues at hand.
I appreciated Vlach's writing (possibly because I fully agree with him) and believe he addresses an issue that many need to study and consider. The Old in the New helped me see more clearly a number of passages that I had often pondered with some element of puzzlement. I found the book to be insightful and very helpful and I highly recommend it as a great resource to all who are diving in to indepth studying of Scripture.