Recently on the Catholic Answers boards, apologist Gary Michuta commented:
"2 Maccabees 12 teaches that those who die in godliness benefit from prayer and sacrifices. Luther was forced to reject (or down-grade) the authority of Maccabees because its meaning unmistakably affirmed Purgatory and all that goes along with it."
I thought it would be interesting to read Luther on this subject:
"But their use of the passage in II Macc. 12[:43], which tells how Judas Maceabeus sent money to Jerusalem for prayers to be offered for those who fell in battle, proves nothing, for that book is not among the books of Holy Scripture, and, as St. Jerome says, it is not found in a Hebrew version, the language in which all the books of the Old Testament are written. In other respects, too, this book deserves little authority, for it contradicts the first Book of Maccabees in its description of King Antiochus, and contains many other fables which destroy its credibility. But even were the book authoritative, it would still be necessary in the case of so important an article that at least one passage out of the chief books [of the Bible] should support it, in order that every word might be established through the mouth of two or three witnesses. It must give rise to suspicion that in order to substantiate this doctrine no more than one passage could be discovered in the entire Bible; moreover this passage is in the least important and most despised book. Especially since so much depends on this doctrine which is so important that, indeed, the papacy and the whole hierarchy are all but built upon it, and derive all their wealth and honor from it. Surely, the majority of the priests would starve to death if there were no purgatory. Well, they should not offer such vague and feeble grounds for our faith!"
Source: LW 32:96
Here's Luther's synopsis of 2 Maccabees. Note his reasoning for rejecting the book, and then compare it with Michuta's understanding of Luther:
Preface to the Second Book of Maccabees (1534)
This book is called, and is supposed to be, the second book of Maccabees, as the title indicates. Yet this cannot be true, because it reports several incidents that happened before those reported in the first book, and it does not proceed any further than Judas Maccabaeus, that is, chapter 7 of the first book. It would be better to call this the first instead of the second book, unless one were to call it simply a second book and not the second book of Maccabees—another or different, certainly, but not second. But we include it anyway, for the sake of the good story of the seven Maccabean martyrs and their mother, and other things as well.
It appears, however, that the book has no single author, but was pieced together out of many books. It also presents a knotty problem in chapter 14[:41–46] where Razis commits suicide, something which also troubles St. Augustine and the ancient fathers. Such an example is good for nothing and should not be praised, even though it may be tolerated and perhaps explained. So also in chapter 1 this book describes the death of Antiochus quite differently than does First Maccabees [6:1–16].
To sum up: just as it is proper for the first book to be included among the sacred Scriptures*, so it is proper that this second book should be thrown out, even though it contains some good things. However the whole thing is left and referred to the pious reader to judge and to decide.
Source: LW 35:352-353
*- Luther comented on 1 Maccabees, "This is another book not to be found in the Hebrew Bible. Yet its words and speech adhere to the same style as the other books of sacred Scripture. This book would not have been unworthy of a place among them, because it is very necessary and helpful for an understanding of chapter 11 of the prophet Daniel."