The only thing I've read by Vidal, and I'm anxious to get some more of his essays -- which I hear are superior to his novels. In any case, he is a great stylist and an exuberant satirist: "[Calvino] knew perfectly well what a mephitic kindergarten our English departments have become..." --'Mephitic kindergarten'!
I skipped three or four of the essays that didn't interest me, and this book lends itself well to selective reading. There is no "numinous theme", as Vidal puts it.
I especially liked the literary criticism and political essays, the latter enumerating and proposing sensible solutions (i.e. an eight-week limit on presidential campaigns) to national problems that, incredibly, prevail today almost exactly as he described them thirty years ago.