These first two books are not a verse-by-verse or chapter-by-chapter commentaries. Rather they both help with understanding how the psalms can be read in our modern day. N.T. Wright is a college level text. C.S. Lewis might be a little easier to read except that it is written in 1950s British English. Both are well worth the work of reading them if you are serious about studying the Psalms.
Each book picture links to its Amazon page.
The following are true commentaries, not simply someone’s devotional thoughts about scripture. They will take a little brain power to read and follow, but well worth the effort. Some of these are available in Kindle versions. remember you don’t need a Kindle to read them just an electronic device that can can run the kindle app. If you choose one of these and get stuck on a word or concept I and others in the church are ready to help you.