Has ever a book started so wonderfully and then died off so quickly? The first 30 or so pages are wonderful, full of striking insights ("Fears and hopes change as history changes, and so do the relations between fears and hopes. But the balancing of fears and hopes is a human constant.") and setting the stage for a mythic book about a mysterious subject.
And then it all dissolves into an incoherent muddle of random observations and overlong discussions. You first begin to wonder when he goes on and on and on about the Oedipus story and in particular the road junction that affected his fate. Eventually, you begin to realize that he is not going to discuss the afterlife of oracles at all, other than how a smattering of later literary figures used them.
The scope of the book is, therefore, a purely literary assessment of oracles. No real input from the realm of history, anthropology or sociology, to say nothing of theology. No discussion of Delphi's real history at all, actually. He does not try to assess the place of Delphi in ancient culture, nor why that changed over time. It is true that his literary references come from a wide range of cultures and periods, but, just because of that, it is not clear how they add up into anything.
Even more frustrating, at least to me, is that two striking things about Delphi that seem to us moderns to be real anomalies - the inaccuracy of some of the oracles and the occasional political corruption of the oracle - are not discussed in any depth. That Delphi urged Athens not to resist Persia, that Athens inverted the oracle to support its policy, and that Delphi was still venerated after Athens won would seem worth a look in, but is ignored.