Cambridge Companions are notoriously inconsistent, since they contain new articles that are frequently non-introductory, so to hit the sweet spot between erudition and accessibility, you have to have scholars and subjects that are wide-ranging enough for the amateur while also sufficient to look good on an academic resume. Some, like the Wittgenstein and Hegel volumes, do remarkably well. This one, however, is a disaster. While some good articles by great scholars appear (Braund, Fowler, Hardie, Zetzel), even the good articles tend to be specialized, and the worse articles are laden with (now-dated) trends of 1997 and will be useless to scholars in 20 years and useless to amateurs today.
Literally half the articles barely touch on Virgil's actual writing, instead focusing on his influence, trends in Virgil criticism, or Roman politics. Fiona Cox's essay on Hermann Broch's Death of Virgil is especially poor, capturing neither the flavor of Virgil or Broch in its eight glib pages and ending with nothing more than a list of other loosely related works of art with almost no commentary.
Martindale's pompous introduction points to him as the culprit: "How Virgil's works are interpreted varies in accordance with the way they are contextualised. And contexts are not self-evident or unproblematic but are themselves constructions composed by juxtaposing texts which in turn have to be interpreted. The third part explores a number of contexts within which meanings - often conflicting meanings - might be determined or generated. And it concludes with a substantial essay on intertextuality. Moreover intertexts - like contexts - do not simply resolve problems of interpretation, they complicate them still more, multiplying possibilities."
The problem isn't that he's wrong as much as that we've heard this a hundred times before. Martindale isn't a particularly good theorist either: a few quotes from Benjamin, Foucault, Steiner, Harold Bloom, and other big names reveal him as a theory dilettante. So the result is Virgil ground through the same textuality mill that has been tail-chasing for decades now.
Among anthologies, A Companion to the Study of Virgil (Brill's Scholars' List) and Why Vergil? A Collection of Interpretations are better on the actual poetry (though nearly anything would be), and A Companion to Vergil's Aeneid and its Tradition (Blackwell Companions to the Ancient World) is better on context and reception, so this book is fairly obsolete. Cambridge should replace it with a better volume. For a nice single-author overview, there's still Brooks Otis' Virgil: A Study in Civilized Poetry (Oklahoma Series in Classical Culture). I'm sure Martindale would call Brooks Otis a hopelessly outdated old fogey, but it's nice to read a scholar who, unlike Martindale, clearly loves literature and language.