Rowland is a personal friend (and my PhD supervisor). He is an excellent thinker, and this is one of the best and most accessible books on covenant theology. The amount of information in the small amount of space is remarkable.
It is a useful book overall, and quite readable; but it may be a question worthy of discussion whether or not the broken covenant of works should be presented as a disruption to God's plan for creation which necessitated the covenant of grace. This is what Dr. Ward teaches: "The covenant of grace is not a separate covenant so much as that development necessitated by the fact that God, confronted by sin, does not abandon his covenanted commitment to his creation but relates to it redemptively" (p. 25). This is in contrast to traditional reformed theology, which taught that the covenant of works was purposefully implemented as a temporary measure. So Samuel Rutherford: "the Lord had in the Law-dispensation a love designe, to set up a Theatre and stage of free grace; And that the way of works should be a time dispensation, like a summer-house to be demolished again: As if the Lord had an aime that works and nature should be a transient, but no standing Court for righteousnesse" (Covenant of Life, p. 3).
It is also questionable whether the covenant of grace can and should be regarded as a development of the covenant of works, seeing as the apostle places them in two antithetical categories from both a metaphysical (1 Cor. 15) and moral (Rom. 5) perspective.