The "Parmenides and Heraclitus" lecture course of 1942-3 is decisive for understanding the relationship between the Greek experience of truth as a-letheia and Heidegger's exposition of Being in Being and Time (the lecture on Plato's Sophist is equally important). This lecture course also helps to clarify Heidegger's relationship with Nietzsche and is essential for a confrontation with the Nietzsche lectures (sp. Heidegger's characterization of the will to power as the will to will). In addition, although Heidegger rarely mentions Hegel directly, this lecture course enters into an implicit dialogue with Hegel's lectures on the history of philosophy. Heidegger's characterization of history as the "transformation of the essence of truth" is momentous. Incidentally, Liddell-Scott defines aidos as "moral feeling, reverence, awe, respect for the feeling or opinion of others or for one's own conscience, and so shame, self-respect." In fact in the detailed analysis it goes so far as to say "personified, Reverence, Pi.O.7.44," that is, it specifically defines the "aidos" mentioned by Heidegger in the 7th Olympian Ode as the personification of reverence. Undermining Heidegger's so-called linguistic analysis/exegesis on the basis of his affiliation with Nazism or Catholocism is a sign of the refusal to take Heidegger's comments to heart.
Heidegger conducts a brilliant tour of Parmenides' fragments, with boatloads of illuminating detours through nearly all of Greek philosophy and history, and much of Western history as well. His insights into the nature of Greek gods and myth, truth as "un-concealment" or "dis-closure", and the development of human thought are indispensable. At times, however, he takes undue liberties - his interpretation of aidos (shame) as "reverence" is particularly far from the mark. As always, the prose is dense, but worth slogging through.