Interpreting James

How shall we interpret the book of James? Among other things that could be said (say, for example, about the genre of James), here is an important word from one of my former professors:

Perhaps no greater mistake can be made in interpreting James than to read his letter in the light of Paul. James, we must remember, is writing . . . before Paul had written any of his letters and probably has no direct knowledge of Paul's teaching. James must be read against the background of the OT, Judaism, and the teaching of Jesus—not the apostle Paul. 

—Douglas J. Moo, The Letter of James (Grand Rapids: Eerdmans, 2000), 83.