Why are so many book summaries built around older works?

When we set about studying the things Christians have said about unity since the writing of the New Testament, we were surprised at just how much God’s people have had to say about it. Unity was important to Christ and throughout Christian history. We found many pastors, theologians, and writers for whom it was also a critical theme. And yet, the church today seems more divided than ever. Rather than reinvent the wheel, we wanted to point to the great Christian theologians, pastors, preachers, and writers who have addressed the topic in the past, highlighting, expounding, and helping modern readers to access these classic works.