Barclay's strengths are his phenomenal knowledge of the Greek language, the Jewish culture and religion, and the Roman occupation during the New Testament era. He is wonderful at conveying this knowledge in a way that simple and easily understandable. He puts it in context so that you can understand what events meant to the people to whom Jesus spoke to 2,000 years ago. His application of those events to modern lives is less successful. Sometimes it works and sometimes it doesn't, but that is the case with a lot of commentary. The historical context is so wonderful that it makes threading your way through the wonky theology worth it. It is really nice to take a long time to go through a gospel slowly and Barclay is a very good way to do it.