Any unusual book that helped you in entrepreneurship?

Not really. One realization is that doing and seeking gradual excellence can be a better teacher than reading (or other forms of un/intentional procrastination). If you happen to learn from someone else's mistakes, that's great. Make lots of survivable mistakes while try to get the fundamentals right... which means you're doing and learning. Learning is the most valuable.

Attitude and schlepping that translate into sales and delivering sh%t cures all. There's lots of annoying and mundane stuff to do, and some things you'll always forget, but it all adds up and you'll get better over time (especially by keeping searchable notes; I have a terrible memory).

Of the books by actual billionaires who have BTDTBTTS , I'd read Felix Dennis' ironically-named How to Get Rich for fun. It contains more of a meta autobiographical attitude insight through stories instead of cargo-cult practices, business theater or phony shortcuts. Supposedly, he claims he was Sir Richard Branson's roommate at one point. Too bad he passed from too hard a life from too much hookers and coke.