Westminster Bookstore has a great deal on the New Studies in Biblical Theology series which is edited by D.A. Carson. It is a solid series that covers a wide range of theological themes within Scripture. You will be hard pressed to find a series of books that accomplishes what the NSBT does. As you can imagine, you save more money as you purchase more volumes within the set. Each individual volume is 40% off. The discount goes up to 50% by purchasing 5 or more volumes and 52% by purchasing the entire set (26 volumes). I believe that this set of books will be a great help to the church for many years.