1. The subjective element of the authors own thought and inner growth needs to be somewhat reflected in the book to interest me personally. But I have read many fiction books that were utterly non-fiction to me cause the deeper philosophical/spiritual elements of his characters reflect truths and ideas that belong to his own experience and growth.

2.The only non-fiction books I can truly remember impacting me was Many P Halls-Secret Teachings of All Ages, basically research into occult and esoteric practices and mans inner development, and carl jungs red book. Otherwise books that impacted me the most have been fiction such as Terry Pratchetts Discworld Novels. Neil Gaiman Sandman Comics,(very profound), paulo coelho the alchemist, alejandro jodorowsky the incal and the technopriests (both comics).

I can't seem to seperate fiction too much from non+fiction. Often times even more personal and deep a fiction novel, than a non-fiction one. You lay bare your inner worlds in fiction :)

I did publish through blurb 2 years ago a compilation of all my poems and short texts I had collected over the years from age 18 until 25. Very turbulent times, but life thankfully only kicks our ass so that we may grow. But at that time I was motivated and inspired to do it, I didn't envision being a perfectionist about it either, goal was just to have it out there so perhaps someone might benefit from something they read in it. Handed out about 100 free copies at the time from my saved money, I was more inspired to share it than to sell it.

If I were you I would do what I feel most inspired and passionate about. And you know best what that is, the end result of a book done with such energy is going to be the most authentic and inspiring. :)