I'm doing quite a bit of work on the Psalms at the moment - partly because I'm down to preach on one of them in a few weeks, and partly because I'm meant to know some of them especially well for my exams next year, so am getting a bit of study in early.
The commentaries on Psalms really are quite an odd bunch. Academic study of the Psalms for ages has centred on the idea of form criticism - when coming to look at any given Psalm, many commentators see their top priority as putting it into one of a dozen or so artificially-constructed categories, which don't always fit that well. Their second priority is then to try to back-engineer the Psalm to work out how it was written, preferably on at least three separate occasions by different people, who were taking earlier material and modifying it. Yes, sometimes there is a good but not conclusive case that that may well have happened (e.g. Psalm 89). Alternatively, they might try to work out what liturgical purpose this Psalm might have fulfilled. If that means inventing new major festivals which there is no evidence for, that seems to be ok as well.
One mind-numbingly obvious problem with all of that is that the Psalms are written as songs to be sung rather than texts to be classified or analysed for redaction layers, but many commentaries don't seem to go much further than that unless they see hints of pagan creation mythology (Psalms 74 and 89), at which point they get all excited.
Given that, four commentators seems to stand out as being worth reading, and two of them weren't in a position to take any notice of modern scholarship, some of which is actually worthwhile. Those four are:
- John Calvin's Commentary on the Psalms (16th century)
- C.H. Spurgeon's Treasury of David (19th century) is well worth a look, especially for the "Quaint Sayings", where Spurgeon has put the best quotes he read on the Psalms.
- Willem vanGemeren in the Expositor's Bible Commentary Series is the best modern commentary I can find on all the Psalms
- Gerald Wilson in the NIV Application Commentary series (Psalms 1-72 only) is remarkable. Wilson spent most of his life studying the Psalms, and in some areas (e.g. Psalm ordering) was a long way ahead of anyone else in the world. It seems that when he was asked to do the NIVAC on Psalms, he threw everything at it. Volume 1 is longer than vanGemeren or Calvin's whole commentaries. Although the NIVAC usually doesn't bother much with scholarship, Wilson throws all kinds of interesting and useful bits in, then applies it, and manages to keep the emphasis devotional. And when I say he threw everything at it, I mean that. He died partway through writing volume 2. This is probably the best commentary on Psalms 1-72, and it is fairly easily accessible to laypeople.
It is quite possible that the multi-volume Baker commentary on the Psalms will be very good, but I haven't seen it yet.