Browsing this book is an excellent experience. Articles vary in length, but provide a good overview in most cases; they also provide further reading on each individual topic.
The price is hefty, but worth it - collecting a series a books covering the breadth of information covered here would be far more expensive. It is not limited to the 'Golden Age', but covers developments in late antiquity - most articles take a historical overview of their topic, not just a snapshot. As an example: the article on the mythical figure of Oedipus does not review the well-known story as given by Sophocles' "Oedipous Tyrannos", but ealier and later versions of the story too.
The fault lies less in the content than in the organisation. If you are looking up a historical or literary figure, then it is fine, but working out what heading a particular topic can be found is an extremely frustrating process. Trying to second-guess an editor seems a pointless exercise; when even a "Thomson Directory" provides a cross-referencing index, how can omitting one here be justified?
In conclusion, this is an excellent resource; but at this price, it feels a little too skimped on production values.