Just a bit breathless and prone to hype all developments as revolutionary, nonetheless, this is an engaging introduction to Delphi and to the recent work that has shown that there was something to the notion of the oracle being in an altered state after all. Decent footnotes and bibliography allow you into the larger set of literature.

There are several guides to each of the ancient sites, this series seems to be backed and written by official archeologists. This book covers the site, going over the various buildings and describing the finds. A short history of the site is included, but this is not the publication for an in-depth history of Delphi and its role in Greek history.