I really enjoy Alister McGrath, his faith journey to Christ is compelling, and he has become a prolific author of apologetics, theology, and biography (his biography of C. S. Lewis is fantastic). In this book he extols the benefits of studying Christian theology. To know theology is to develop a habit of discernment, to see the world, people, and things rightly, properly, and fully. Theology provides a big picture perspective, providing a guide to the study and understanding of Bible verses, chapters, or books.
McGrath also challenges the reader to not only learn about the great Christian theologians and philosophers of history, but also to let them teach you how to live and think in a Christian way today. Finally, he provides resources on further reading in theology. Overall I believe this is a very worthy read.