Here is a list of the most important books that have shaped the way I think.
I’d highly recommend any of these.

The Slight Edge by Jeff Olson
The Subtle Art Of Not Giving A F*ck by Mark Manson
The Life-Changing Magic Of Tidying Up by Marie Kondo
Mach 2 With Your Hair On Fire by Richard Bliss Brooke

Man’s Search For Meaning by Viktor E. Frankl
The 10-Second Philosophy By Derek Mills

The Richest Man In Babylon by George S. Clason
Elite Minds by Dr Stan Beecham
Tribe Of Mentors by Timothy Ferris
You’ll See It When You Believe It by Dr Wayne W. Dyer
How To Talk To Anyone by Leil Lowndes
Bigger Leaner Stronger by Michael Matthews
The Tao of Pooh by Benjamin Hoff
Small Gods by Terry Pratchett

One Robe One Bowl – The Zen Poetry of Ryokan 
Debretts A-Z of Modern Manners