There may be some conjecture out there about what Luther said about this or that book, but it does seem according to my research, at least with regard to the book of James, that he would like to have nixed it from teaching use if not throw it out of the canon:***We should throw the epistle of James out of this school ***Wittenberg], for it doesn’t amount to much.*It contains not a syllable about Christ. Not once does it mention Christ, except at the beginning.*I maintain that some Jew wrote it who probably heard about Christian people but never encountered any.*Since he heard that Christians place great weight on faith in Christ, he thought, ‘Wait a moment!*I’ll oppose them and urge works alone.’*This he did. He wrote not a word about the suffering and resurrection of Christ, althought this is what all the apostles preached about. Besides, there is no order or method in the epistle. No he discusses clothing and then he writes about wrath and is constatntly shifting from one to the other.*
He presents a comparison: ‘As the body apart from the spirit is dead, so faith apart from works is dead.’ O Mary, mother of God!! What a terrible comparison that is!!!!
LW, 54, 424-425
Elsewhere he explicitly said James had errors in his theology:*James argues in his letter (Jas. 2:21) that Abraham was justified on the basis of his works. Because the text says:
Now I see that you are righteous', he wants to conclude from this that previously Abraham was not righteous. . . . .Abraham was righteous by faith before God acknowledged him as such. Therefore **James*concluded falsely that now at last he was justified after that obedience***,*for faith and righteousness are known by works as by the fruit. But it does not follow, as James raves: Hence the fruits justify’ just as it does not follow: 'I know a tree by its fruit; therefore the tree becomes good as a result of its fruit.
Therefore let our opponents be done with their James, whom they throw up to us so often(Luther 4:134).*I believe that last quote is from Luther’s Works.Saw these quotes
here a while back. I’ve also seen part of the latter quote
cited as LW 4.26)