There are though various other problems authenticating Luther's writings. One interesting example is his work on Genesis. Luther spent quite a number of years involved lecturing on Genesis (1535-1545 and perhaps earlier periods as well). The very first volumes of Luther's Works in English begin with his material on Genesis. The editors point out some of the difficulties with authenticating these writings:
For as we have it, the work is not a product of Luther’s pen or even a transcript of his lectures; it is a transcript that has been reworked and edited. From the instance of other commentaries, where we have both the lecture notes and the printed version, it is evident that the editors of Luther’s Biblical commentaries allowed themselves greater liberties in preparing his lectures for publication than the modern conventions of editing and publishing would justify (cf. Luther’s Works, 13, Introduction, pp. xi–xii). Where we have only the printed version, therefore, we have reason to be on the lookout for marks of redactorial additions and changes. There are such marks in the Lectures on Genesis, as Peter Meinhold, the leading scholar to concern himself with them, has pointed out. Now and again, for example, there are admonitions addressed to the “reader” even though this purports to be a lecture (thus See p. 16, note 29). We have already referred to the presence of historical allusions that are clearly anachronistic and are apparently inserted by the editors. A remarkable circumstance is the accuracy with which most classical citations are quoted. Luther had an astonishingly retentive memory, as his Biblical quotations show. He had also read around in the classics and knew some classical works almost by heart. But the citations here in Genesis are almost uniformly accurate; and where a comparison of lecture notes with printed version is possible, it becomes evident that the editors took a chance phrase or allusion from Luther’s lectures and amplified it into a full-blown and accurate citation. Some citations from classical authors do not even have a chance phrase or allusion as their foundation but were inserted by the editors because they seemed to fit. Because of this we are in no position to determine with any degree of finality which of the classical quotations originated with Luther and which did not. The same thing is true of quotations from Christian authors. It is beyond doubt that Luther had read widely in the works of St. Augustine; therefore many, if not most, of the references to Augustine seem to be based on his own reading. Other authors, too, he had studied, as his completely authentic works clearly show. From repeated references we know of his regard for Nicolaus de Lyra, on whom these Lectures on Genesis are dependent for the rabbinical learning they display and for at least some of the patristic exegesis they consider... We know, too, that in 1509–10 Luther had lectured on the Sentences of Peter Lombard, to which he also makes reference in this commentary. But we cannot be sure how many of the quotations even from these works are actually his own. The problem of authenticity and integrity becomes most acute, however, not in the question of Luther’s erudition but in the question of his actual theological position. And the researches of Peter Meinhold have led him to the conclusion that the theology of the Lectures on Genesis has also been adulterated by the editors to conform it to the growing orthodoxy of the second generation of Lutherans. He bases this conclusion on a study of the theology of Veit Dietrich in relation to both Luther and Melanchthon; in several cases he has proved that Dietrich’s brand of Melanchthonian theology has been superimposed upon Luther’s thought and language, and in other cases he has shown that this is very likely. This has led him to a rather profound skepticism about the reliability of the Lectures on Genesis as a source of information about the thought of the old Luther.
Luther, M. (1999, c1958). Vol. 1: Luther's works, vol. 1 : Lectures on Genesis: Chapters 1-5 (J. J. Pelikan, H. C. Oswald and H. T. Lehmann, Ed.). Luther's Works (1). Saint Louis: Concordia Publishing House.
An interesting footnote to this problem is the work of Dr. Mickey L. Mattox, Defender of the Most Holy Matriarchs: Martin Luther's Interpretation of the Women in Genesis in the Enarrationes in Genesin, 1535-1545. (Brill, 2003). This book, unfortunately, is rather expensive. In an appendix he addresses further research into Luther's Genesis material and argues that the material is genuine Luther. He argues the editors that put the work together were indeed faithful to the real Luther. His analysis of the alleged anachronisms in the text are fascinating, and worth a mention in any revision of LW 1-8. Elsewhere Mattox has commented, "We also know a lot more today about the process by which Luther's lectures were edited and published, and the upshot of that work is to confirm that publications like the Genesis Lectures bring us the voice of Luther if not in each and every case in the ipsissima verba, then at least very much as he himself wished it to be heard."