Existential loneliness
For genre distinctions, this book is a memoir about its author's life and struggles. But, once the readers learn of the unimaginable situation from which the author writes the book, they will see what is remarkable about it. Because he worked so hard to communicate even through his nearly-complete paralysis, now the reader sees an account of what it is like to be so severely paralyzed that one cannot even speak. We see that he is enduring a religious experience of true loneliness. His candid reflections are automatic philosophy because he is a martyr of witnessing one's point of view but not being able to communicate about it. Even in his book, there is an existential loneliness that permanently separates the reader and the author. These kinds of reflections define the memoir.
Art as legacy
So if the book fails to bridge the existential gap between author and audience, then why does this author go through such lengths to make this book a reality? The answer seems to be related to legacy. It is not about communication alone; the book stakes a claim for the man's legacy. As a piece of art, he hopes this book will be some permanent artifact of his life, and not just his life after the stroke, but his life before the stroke which was deeply artistic and reflective. He discusses his emotional connection to the arts.
Fate and God
Throughout the book, the author spirals off into lengthy discussions about fate and God. This is on his mind for obvious reasons. His condition is so medically bizarre that it isn't in the doctor's medical textbooks. From the outside in, he seems completely comatose, unable to speak or make facial expressions. The fact that he has any ability to communicate whatsoever is a testament to his cleverness; he is only able to blink with his one eye (they sew his other eye shut!) and by blinking, he selects letters from a queue. This situation is so dire that he cannot stop himself from talking about God, about reality, and about the human experience which is so diverse and fascinating, and which sometimes put people in these bizarre situations where they are forced to experience reality from a limited point of view.
