You can name multiple books though if that is the case with you.
Man's Search for Meaning by Viktor Frankl is a close second. I read this when I was going through a particularly difficult time in life, and it has stuck with me since.
David Deutsch's The Beginning of Infinity definitely changed how I look at skepticism and pessimism in general (a weird take-away, I agree).
There's only one book that I often find myself going back to, which is Hermann Hesse's Siddhartha. It's a very profound work IMO, and provides a sense of grounding to me.
Re-reading it in my late 30s blew my mind. I wish I had the words to describe why. Best I can do is that it solidified (dare I say explained) many of the spiritual aspects I have been struggling with lately.
Thinking, Fast and Slow by Daniel Kahneman is just generally a really interesting book and impacted the way I view decision-making.
The Wind-Up Bird Chronicle by Haruki Murakami really opened my eyes to unconventional plotlines and surrealist/magic realist themes, and in doing so greatly impacted my exploration and enjoyment of literature and other art.
This is a book on how to learn anything and nothing really about guitar. It distills the zen approach to life in a very usable way. I made a major career shift to ML research using the lessons I learnt from this book
The Gita It helped me develop depersonalised thinking and to some extent the ability to view people equanimously. I feel it has helped me accept and become a lot more inclusive person than who i was before i read it
- Love in the time of Cholera by Gabriel Garcia Marquez: explores love in it's many forms.
- Lonesome Dove by Larry McMurtry: about love, the absurdity of life, beginnings and ends.
- Miles by Miles Davis, Quincy Troupe: about jazz and the life of it's greatest creator.
- Prometheus Rising by Robert Anton Wilson: ramblings of a pope.
I was given it at what seemed far too young an age (about seven i think) by a slightly crazy neighbour who had no idea what books would be suitable for me (a year later he gave me an adults book on space based weapons exploring the physics etc). Despite it being a stretch, i was mad about sci-fi films and the book made me start thinking about what i was seeing, and introduced me to huge range of ideas (FTL travel, time travel, parallel universes, genetics, terra forming, environmental concerns, computers, robotics) well before i would have encountered them otherwise and it was discussed in a serious considered way.
I read in it about a thousand things I'd experienced but I'd thought were impossible to describe. It was written to inspire people, and inspired me daily for many years—nay, eternally! It—and Emerson's other writings, e.g. Representative Men, Conduct of Life, Nature, Addresses and Lectures etc—gave all the drops of my blood eyes that look upwards.
In my mid twenties, this book helped me pay off all my student loans and build an emergency fund with 4-6 months of runway. It changed the way I think about money.
I Will Teach You To Be Rich by Ramit Sethi.
This built on top of Dave Ramsey’s by helping me create a system to build my wealth through investing and still continue to save towards future goals/emergencies.
"Science is far from a perfect instrument of knowledge. It's just the best we have."
His telling of the story of man's grappling to conquer flight really helped me to understand how I should approach grappling with my own challenges.
I haven't read it in a while, but Siddhartha by Hermann Hesse, resonated with me a lot and I (used to) read it every so often to stay humble and focus less on winning life and more on enjoying it. It's a short read and I recommend it often.
The Elements of Typographic Style, though I'm yet to finish it, has helped inform my view of text layout in every day life.
Never Split the Difference will definitely continue to be useful in terms of negotiating all kinds of situations in life.
Pushing to the Front by Orison Swett Marden
Meditations by Marcus Aurelius
I'm still working my way back in time, but so far these three are great!
How to Win Friends and Influence People taught me that negotiation is not adversarial, and that most businesses is about mutual respect.
Surely You're Joking, Mr Feynman made me want to be more curious and more adventurous. Not to be successful, but to have an interesting life.
Small book, small words, short sentences but separates the wheat from the chaff of thinking and understanding. If you're fond of horoscopes, this is not the book for you.
There are other books like anything by H.P. Lovecraft, Kevin Mitnick's books and "The Cuckoo's Egg" by Clifford Stoll that has also stuck with me and changed how I think about things.
Not only was it a terrific read, it changed my life for the better and I believe it has made be a better, happier person.
The Global Empire by Alexander Bard & Jan Söderqvist.