If you want an excellent overview of NT Theology without having to wade through the typically thick NTT books out there, you can really do no better than Thomas Schreiner's Magnifying God in Christ (MGC). MGC is a summary of his thick New Testament Theology (which should also be on your shelf). The title hints at the thematic approach Schreiner takes in his book. He observes, "It is illuminating to consider NT theology from a twofold perspective. First, God's purpose in all that he does is to bring honor to himself and to Jesus Christ. The NT is radically God-centered...Second, the centrality of God in Christ leads to abstraction if it is not closely related to the history of salvation, to the fulfillment of God's promises...The NT unfolds the fulfillment of the promises made in the OT...Hence, contrary to what some have said, God's glory and humans' salvation are not in conflict. Rather, God is glorified in the salvation of his people" (16).
Schreiner writes with a scholarly clarity. His interactions with opposing views are up to date. While he is an academic, he treats his subject
From a confessional Reformed view it is helpful to interact with Schreiner's use of the law. The traditional Reformed three-fold use of the law will be challenged to some degree. See his 40 Questions book regarding the law for more detailed treatment of the subject. This does not detract from the book's usefulness, however. Much of Schreiner's discussion of the law is valuable; due consideration should be given to Schreiner's interaction with the New Perspective. Also helpful is the author's treatment of faith and works with relation to Romans and James.
In sum, Schreiner demonstrates how the NT writers contribute to the theme of God's glory in Christ in the salvation of sinners. This summary volume is an intellectually stimulating and spiritually invigorating read as Schreiner navigates through the NT which magnifies God in Christ. The larger NTT is excellent for the office and MGC for the bedside table.