Most scholars agree that Galatians was written about 50 A.D. and is therefore among the earliest, if not the first, of the New Testament documents. The first Christians were Jewish but as the gospel spreads more and more Christians come from non-Jewish backgrounds. This creates some serious problems for the early church not least of which is do you have to be a Jew first before you can become a Christian? Although this may seem an esoteric issue to us today it raises an absolutely central question for all Christians – what is the gospel? For commentaries on Galatians see http://bestcommentaries.com/galatians. This site gives you reviews and some indication of the academic level of each commentary (ie technical, pastoral, devotional).