Just finished Richard Longenecker's 1964 Pauline theology text. It is, I think, the best book on Paul I've (yet) read. (And no, I don't think Sanders is fair to it on pp. 56-57 of Paul and Palestinian Judaism. Longenecker was remarkably balanced in his groundwork on Early Judaism, especially in light of the fact that he wrote pre-New Perspective, and did not succomb to the imbalanced view of Weber/Boussett/Billerbeck, as Sanders asserts.)
He writes in a very clear and balanced way; his explanation of Romans 7 is very convincing (I think he may have converted me from post-conversion bio to neither pre- nor post-conversion but an argument for human inability in a post-fall, law-existent world); his understanding of continuity/discontinuity in OT/NT is very helpful; his sections on "in Christ" and "the law of Christ" are extremely illumining; and I think he gets the balance between law and freedom in the life of the Christian just right.
I don't agree with everything; and he's a bit too Lutheran for me at times. But it is just excellent. So many light bulbs went on for me as I read.