Most Bible scholars think Jesus's brother wrote the book.
James didn’t become a believer until after Jesus’ resurrection.
His letter was written to the Jewish Christians, challenging them, very strongly, even bluntly, to live out their faith in their everyday lives.
James 2:1-4
James 2:5-7
James 2:8-11
James 2:12-13
James 2:14-17
James 2:18-19
James 2:25-26