Re: One book which changed your life
A little book called "The Rudiments of Music" taught me to read and speak the language of musicians.
Around the turn of the century The Idiots Guide to HTML sent me on a path of web design; until then I didn't know where to start in creating a "legit" (ie. non Homestead) website. That was followed by years of happy hobbying plus some graphics work for a while.
Philosophically, no one book. Lots of self help, popular psychology and Buddhism books when I was young - the ones that started me were "Your Erroneous Zones" and "I'm OK, You're OK". I've since spent many years gradually shooing out the many bats in my belfry - it's a work in progress.
I only recently noticed "how we've been programmed from birth to accept principles and understandings which are incoherent and contradictory", mainly from listening to rationalist speakers on YT. I was amazed to notice all the archaic and illogical misconceptions that I once simply accepted as fact - they were really programmed into me and never questioned.