This series of classes was given by by Swami Prabhavananda on the path to God through knowledge as taught by Shankara. The basic teaching is that God alone is the all-pervading reality; the individual soul is none other than the universal soul.
The teachings are what Vedanta is all about, and they're given in a way that makes sense to a Western audience.
The classes represent the swami at his best, and the questions after the class could cover anything and are not to be missed.