Did Luther add a word to Romans 3? There are many who have pointed out that Luther added the word, "alone" to Romans 3:28 (you can read one such example in this question) so that the Luther Bible reads:


  for we reckon a man to be justified by faith alone without deeds of law


where the Greek reads:


  for we reckon a man to be justified by faith without deeds of law


Is this true?
Yes and no. Yes he added it, no it is not the atrocity that it necessarily implies.

Part of Luther's defense of the translation is that inclusion of the word "alone" is more grammatically correct than its exclusion. While I'm not an expert in German, I do speak enough of it to know that he does have a point.

His problem, though, is in the interpretation of the verse. If we're being true to the original Greek the passage is better understood, "of the set {faith, works of the law} man is only reconciled by faith."