This letter (that's what an epistle is) was probably the earliest of the New Testament books to be written. MacArthur and others place the date between AD 44 and 49,the time that Stephen was martyred (circa AD 44) and the Council of Jerusalem (circa AD 49). Persecution and the scattering of the believers is mentioned immediately by James whereas the important Council meeting recorded in Acts chapter 15 is not. Those bookend experiences help set the date.
James himself is an interesting person to consider. Was he the half-brother of Jesus (the son of Mary and Joseph)? It seems likely. Acts chapter 12 specifically names two men named James. The first is the brother of John that was martyred by Herod (v. 2) so that particular James (one of the fishermen-disciples: Peter, Andrew, James, and John) probably could not be the author of the book. The second is someone in authority to whom Peter was to report after being freed from prison by an angel (v. 17). This second James was the pastor of the church at Jerusalem. It makes sense that Pastor James would be the author as this letter seems to be written by an under-shepherd concerned for his scattered flock. Besides the fisherman-disciple James, the son of Mary and Joseph fits the profile much better than James the Less or James, the father of Judas (not Iscariot), which are the only other men by the name mentioned in New Testament Scripture. By process of elimination most scholars believe the author to be Jesus' half-brother.
We know from the gospels that the brothers and sisters of Jesus did not believe him to be the Messiah during the years of His ministry. What changed James' mind? The Resurrection would be powerful proof that Big Brother is who He says He is! We're told in I Corinthians 15:7 that Jesus appeared to a man named James, presumably the one that everyone recognized as the Jerusalem pastor.
On a personal note, I am touched by the love of Jesus for his earthly siblings. They thought He was crazy when he was publicly picking fights with the religious and political leaders. At least once they tried to quietly talk him into coming home with them. One can almost feel their embarrassment caused by this "odd" brother. (Something to think about: their family's "black sheep" was actually the pure Lamb of God.) After the Resurrection Jesus sought them out and forgave them of their sins. Two of them - James and Jude - were privileged to have their letters preserved as scripture. I'm so glad Jesus forgave them and changed them into outspoken representatives themselves. Like them, I have a Big Brother who intercedes to our Father on my behalf even though I also don't deserve to receive family status.
Enjoy the book! And join me, if you can, in memorizing portions of it.