This poem clearly earns its reputation as a dark and difficult work.  Eliot draws heavily on classic sources (Dante, Shakespeare’s  The Tempest, Sophocles’ Oedipus, Buddha, St. Augustine, Ovid) as well as more contemporary work (Wagner, Hesse) in this work that uses juxtaposition (memory and desire, April and cruel weather) to decry the deterioration of the post-WWI world.  Death, dirt, decay, the desert, bad weather all figure in his theme of loss.  By citing classic sources, Eliot indicates his conviction that only through learning, erudition, wisdom, and higher virtue can the world recover its pre-WWI innocence and values.  Difficult read, even with the pages of footnotes, but a good introduction to the modernist themes and techniques.