The literature on the New Perspective on Paul is vast, to say the least. There are volumes supporting and extending Sanders’ work, there are others critiquing his work. Some are aimed at N. T. Wright as a particularly popular proponent of the New Perspective, others championing the classic Reformation view with zeal worthy of Elijah. Since Wright has sold quite a few books and has attracted a strong following, it is somewhat fashionable to reject him ought of hand with a sneer usually reserved for Rick Warren. This does not seem fair to me since Wright is a brilliant scholar, careful researcher and entertaining writer.
Mark Seifrid has been a strong voice in favor of a more or less traditional view of Paul. His Christ, Our Righteousness: Paul’s Theology of Justification (Downers Grove: Intervarsity, 2000) is a brief treatment of the topic but among the very best and most accessible for the layman. Seyoon Kim engages James Dunn in his Paul and the New Perspective: Second Thoughts on the Origin of Paul’s Gospel (Grand Rapids, Mich.: Eerdmans, 2002). Stephen Westerholm’s Perspectives New and Old on Paul (Grand Rapids, Mich.: Eerdmans, 2004) surveys Augustine, Luther, Calvin and Wesley as well as the “Lutheran” interpreters of Paul in the twentieth century before turning to Paul’s view of the Law and Justification in the final third of the book. This historical approach seems backwards to me, but it really does “work” in practice. Francis Watson recently revised his Paul, Judaism and the Gentiles (Grand Rapids, Mich.: Eerdmans, 2007), attempting to break through the false dichotomy between either the Traditional “Lutheran” view nor the New Perspective. In many ways, Watson’s work draws the best from both views of Paul and attempts to build a biblical theology of Paul. I would also add Douglas Campbell’s The Deliverance of God: An Apocalyptic Rereading of Justification in Paul (Grand Rapids, Mich.: Eerdmans, 2009), although it has been severely critiqued. Matlock, for example, called the book an “impossibly forced argument” (R. Barry Matlock, “Zeal for Paul but not according to Knowledge: Douglas Campbell’s War on ‘Justification Theory,’” JSNT 34 (2011): 115-149. See also Joshua Jipp, “Douglas Campbell’s Apocalyptic, Rhetorical Paul: Review Article,” Horizons in Biblical Theology 32(2010): 183-197; Douglas J. Moo, “The Deliverance of God: An Apocalyptic Rereading Of Justification In Paul By Douglas A. Campbell, Review Article,” JETS 53 (2010): 143-50.)
While studies challenging Sanders’ position are not unique, they are almost always from the Calvinist side of the Reformation and are intent on defending the reformation view of justification by faith in Paul. Chris Vanlandingham has charted a new course in that he approaches Sanders from a decidedly Arminian view of salvation and the last judgment. For Vanlandingham, Sanders is guilty of the very sins of which he accused scholarship in his Paul and Palestinian Judaism – he reads the Reformation view of grace and works back into the literature of the Second Temple period and finds a robust view of election. Vanlandingham contends that Jewish literature of this period uniformly describes the final judgment as a judgment by works, including the Apostle Paul. (See Chris Vanlandingham, Judgment and Justification in Early Judaism and the Apostle Paul. Peabody, Mass.: Hendrickson, 2006.)
Another dozen titles could be added to this list if I included responses from systematic theology, but these are among the best which I have read on the New Perspective and are all worth reading to balance the more polemical books out there. This is far from a complete list of responses to the New Perspective; please feel free to suggest others in the comments.