I started Justification and Variegated Nomism, Volume 2: The Paradoxes of Paul.
In his essay, "Paul's Use of Righteousness Language Against Its Hellenistic Background", Mark Seifrid contrasts Martin Luther's view on justification with that of Philip Melanchthon. What I got out of Seifrid's discussion was that Melanchthon limited justification to a legal declaration by God that a believer in Christ is righteous, whereas Luther thought that justification was both a divine declaration and God's effective divine word of creating the human being anew, setting him on a path on which sin is overcome "until at the end of our earthly life it is finally removed" (page 70). So, in a sense, Luther believed that justification was both God declaring the believer righteous and also commencing the process of making him righteous. Melanchthon, however, considered the believers' obedience to the law "an independent, subsequent divine action in the life of the believer", in which the believer "now cooperates with grace rather than solely being operated upon by God" (page 69). Seifrid still states that "Melanchthon was willing to speak of the necessity of good works for justification".
So did Luther link justification with sanctification, whereas Melanchthon divorced the two? If Luther indeed did that, I doubt that he did so in the manner that Protestants accuse Catholics of doing: of creating a situation in which believers need to protect on a continual basis their standing before God, through rites, repentance, etc. Rather, my guess is that, for Luther, God declares a believer righteous on the basis of the believer's faith, and so the believer can be spiritually secure for the rest of his life; and yet, when God declares that believer righteous, he also begins a process in which the believer becomes righteous on a practical level. Melanchthon may have had the same concept, only he considered that process to be apart from justification, plus he may have ascribed to the believer more of an active role in becoming practically righteous.
Whether Seifrid is right on this or not, I don't know. I have long understood Luther's position to be what Seifrid says was Melanchthon's position. But there is another area in which Seifrid challenged what I thought I knew about Luther. My understanding is that Luther believed that justification is when Christ got my sins imputed to him on the cross, whereas God imputes to me (a believer) Christ's righteousness. You know the song "Cover with His Life", or the evangelical statement that, when God looks at us, he sees Jesus' righteous life, and God then treats us as Jesus deserves? That's how I understood Luther. Seifrid states on pages 70-71 that "Luther understands justification in terms of the alien righteousness granted in believing union with Christ: our sins belong to him, his righteousness belongs to us." But Seifrid then goes on to say that Luther thinks righteousness is imputed to the believer, but he does not speak specifically of the "imputation of Christ's righteousness." According to Seifrid, such language pops up occasionally in Melanchthon's writings, but it came "into widespread usage only after the Osiandrian controversy (1551), when Protestants found it necessary...to define more precisely how one ought to speak about justification" (page 71). So I'm confused.
UPDATE: Henri Blocher says in his contribution to this volume that Melanchthon started with the view that justification was forensic and also involved an inward transformation, but he "began to sharpen his elucidation of the term" (page 491).