Herzog's unfinished academic book is a perfect symbol of how Herzog does a whole lot of thinking and very little acting. It's part of his job as a professor to do research and to publish books, but he can barely describe what he's writing about, let alone sit down and write the thing. As one passage tells us,
Herzog tried to explain what it was about—that his study was supposed to have ended with a new angle on the modern condition, showing how life could be lived by renewing universal connections; overturning the last of the Romantic errors about the uniqueness of the Self. (2.67)
What the what? How much of that makes sense to you? And there's a reason it whooshes over our heads like a bat out of hell: Herzog doesn't himself know what (in any kind of concrete manner) he's writing about. He can't summon the motivation to finish the project. Instead, he drags his wife to the country so he can try—and fail— to finish this project.
His inability to get the thing done definitely has a disastrous effect on both his failed marriages, as well as being symbolic of the fact that Herzog manages to be both astoundingly locked within his head and unable to make the time spent in his brain-prison useful in tangible way.