10 of those

Luther’s Works: The American Edition, published by Concordia and Fortress Press between 1955 and 1986, comprises fifty-five volumes. These are a selection representing only about a third of Luther’s works in the Latin and German of the standard Weimar Edition, not including the German Bible.

When Luther was prevailed upon to write a preface to the projected complete edition of his Latin writings in 1545, about a year before his death, he took the opportunity to review the high points of his career—to show that he really never had the time and talent to produce literature worth preserving, that in publishing these works he was now merely yielding to his friends' argument that his works would be published in any case, if not with his cooperation, then possibly by men who had no real understanding of them. 

That was one thing. But in that preface Luther also implored the reader of his Latin writings "for the sake of our Lord Jesus Christ Himself to read those things judiciously, yes, with great commiseration". With Luther's lectures on the Epistle to the Romans he had a splendid opportunity to share with his students the great find of his life, "that place in Paul which was for me truly the gate of Paradise."