In chapter 7 of Is There Anything Good About Hell?, I argue briefly that there are degrees of punishment in hell precisely because there are degrees of sin.
It is a serious error of Christian doctrine to make all sins equal in the sight of God, and it is surprising just how prevalent this error is in Christian circles. If all other things are equal, rape is more heinous to God than lust, although both are sins of sexual violence. Murder is more abhorrent to the Lord than anger, though they are cut from the same cloth (Mt 5:21–22, Jas 4:1–2). False teaching is more odious than ignorance, though they are offspring of the same deceiver. What is important in light of the variation in hell’s degrees of punishment is that we preserve the truth that “whoever keeps the whole law but fails in one point has become guilty of all of it” (Jas 2:10).
Recently, I stumbled across an excellent and concise essay at The Gospel Coalition by Albert Martin and Fred Zaspel that does an excellent job of explaining the rationality of hell’s degrees of punishment. It probably doesn’t warrant an entry into the literature database, but it is worth a bit of your time. Some excerpts are selected below.