Many have asked for the reference for Luther's quote, which states that St Paul and St James stand in contradiction with one another on the doctrine of justification. You can find it in:
Preserved Smith's The Life and Letters of Martin Luther on page 269. Published by Houghton Mifflin Company, 1911.
Yes the man's first name is "Preserved."
For your awareness, I provide a few more authentic quotes from Luther:
Therefore St James' epistle is really an epistle of straw, compared to these others, for it has nothing of the nature of the Gospel about it.Now let me ask any devout Bible-believing Christian whether these words honor the infallible and Holy Spirit inspired words of the canonical Epistle of St James.
(Luther's Works 35, 362)
The epistle of James gives us much trouble, for the Papists embrace it alone and leave out all the rest...Accordingly, if they will not admit my interpretations, then I shall make rubble also of it. I almost feel like throwing Jimmy into the stove, as the priest in Kalenberg did.
(Luther's Works 34, 317)
We should throw the epistle of James out of this school [i.e. Wittenburg], 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.
(Luther's Works 54, 424)