One of my favorite quotes is from George Bernard Shaw who said, “The reasonable man adapts himself to the world; the unreasonable persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.”
Writing books as a self-publisher depends heavily on writing books that are reasonable, however. You want to write books that people want and are searching for. If people aren’t searching for it, then they won’t find it (without marketing). Writing a very unusual book as a self-publisher makes the chance of people finding it slim. However, everyone writes books people are searching for, so you need to be unreasonable just enough to stand out from the others (niche).
Write a book people are searching for (reasonable) that stands out just enough to generate attention, pulling customers away from the mainstream (unreasonable).
Find the balance to be both reasonable (to be easily found), and unreasonable (to stand out).