May be a good concrete question to pursue?

I am so much preoccupied with the question of What would I like to write about in my book? Am I supposed to write a book? A book is a means to convey your wisdom, your knowledge to people, to others who may not know about some lessons you have learnt through your life. The question reminds me of a video lecture by Prof. Meister, a well-known scientist in visual system, where he said something like, "In the past, I was wondering what we wanted to write in textbooks for students to know about visual system. After years of research in visual system, I am now writing my new discoveries into the classic textbook (the Abbot&Dayan book that Neuroscience students read in their first semester)". I remember I paused the video for a moment, as I was amazed how long-term he had been thinking when he was doing his repetitive experiments in a dark lab. It naturally made me ask, "what do I want to add to textbooks?". I shrugged. Somehow undecided if I want to add anything in this area. That was an alert, indeed. The hard one to tackle. I consciously decided to keep it hidden for a while in a blind spot in my memory until it suddenly emerged a while ago when I was checking my Amazon Wish list and felt overwhelmed by noticing the large number of books I had added, from history books, to art, literature, psychoanalysis, mythology, religion, and to languages and writing. Let alone the current books I have on my bed stand on Education and on Culture. There are so many good books written by knowledgeable people who try to make a contribution to the world by helping people learn a new dimension of their life. What would you write about then? About visual system? Boring! We already know so many things about how we see. It is not a mystery anymore. So why is it that you moved to this field? I did not want to philosophise how the brain works with some colourful FMRI images, I wanted to see how neurons actually respond. Sensory systems are the simplest place to kick off. Well, it is just about different levels. Vincent would probably say, you won't learn how the brain works if you do not know about microstructures like genes - the level I cannot care less about. Again, If you spend your life on Visual System, you ought to write about that subject. It's boring! Well, this repetitive dialogue might indicate I should put back the question to the unconsciousness. OR, it might be a good concrete question to help me figure out what I'd like to spend most of my time on. In any case, asking good questions are very important in science. As it is in life. Then, could this be a good one: "What would I like to write about in my book(s)?"?