Is the book of Psalms a prophetic book?
Yes. The Psalms are loaded with prophecy, just as much as Isaiah and Daniel, and are rightly considered a book of prophecy as well as a psalm. David, being a prophet, spoke beforehand of the resurrection of Christ, quoting Psalms that refer to Christ rather than himself.
Les teaches that most people do not think of prophecy coming out of the Psalms, but they are loaded with prophecy just as much as Isaiah, Daniel, and the rest of them. It is a book of prophecy as well as a psalm. In Acts 2, Peter explains that David was a prophet, and David was not speaking of himself, because David was dead and buried. Instead, David foresaw and spoke of the resurrection of Christ, and God had sworn with an oath that He would raise up Christ to sit on David's throne.