Anxious and Educated
You get the best sense of this book's overall tone when you read the letters that Moses Herzog writes to all kinds of people, both living and dead. He even writes to Nietzche, for Pete's sake:
Dear Herr Nietzsche […] You speak of the power of the Dionysian spirit to endure the sight of the Terrible, the Questionable, to allow itself the luxury of Destruction, to witness Decomposition, Hideousness, Evil. (9.21)
Yeah, it's safe to say that this letter is the ranting of a very educated (maybe over-educated?) guy. It's also safe to say that anyone writing to a dead philosopher has either lost—or at least misplaced—his marbles. He's more anxious than a puppy during a thunderstorm: check out those scary capitalized words.
And this tone doesn't go away, even when he writes his (very much alive) lover Ramona:
Dear Ramona, you mustn't think because I've taken a powder, briefly, that I don't care for you. I do! I feel you close about me, much of the time. (3.3)
As you can see, Herzog is perma-formal (check out that "mustn't"!) dude. Herzog's problem is that even with all the intelligence in the world, the one thing he doesn't know is what he actually wants out of life. And you can feel that anxiety as he rants on, eloquently and eruditely, throughout this book.