Getting Things Done - David Allen. If you have adult ADHD like me, and you haven't read this, it's the first system that's really worked for productivity for me.
Man's Search for Meaning - Victor Frankl.
Living Buddha, Living Christ - Thich Nhat Hanh.
Cosmos - Carl Sagan.
The Left Hand of Darkness - Ursula K. LeGuin.
The One who Walks Away from Omelas - U.K. LeGuin.
Wild Seed - Octavia Butler.
The Heike Monogatari - (tr. Helen Craig McCullough) “The sound of the Gion Shoja temple bells echoes the impermanence of all things; the color of the sala flowers reveals the truth that to flourish is to fall. The proud do not endure, like a passing dream on a night in spring; the mighty fall at last, to be no more than dust before the wind.” If you need a comparison. this is the Japanese historical equivalent of Game of Thrones combined with a bit of MacBeth. The rise and fall of two shogunate families, and an analysis of the tragic flaws of character that brought their fall about.
Les Miserables - Victor Hugo.
Small Gods - Terry Pratchett.
Heart of Darkness - Joseph Conrad.
The Guide - R. K. Narayan.
Evidence - Mary Oliver.
All of Us - The Collected Poetry of Raymond Carver.
Silence - Shusaku Endo.
The Great Gatsby - F Scott Fitzgerald.
The Wind-Up Bird Chronicle - Murakami Haruki. This and the next four are odd choices, perhaps, since it's a surrealist book, but IMO books that force your imagination to work hard do as much for creativity and fresh ideas as any of the more popular methods.
The Well-Built City (The Physiognomy / Memoranda / The Beyond) Jeffery Ford - Surrealist novellas best described as about the protagonist living and achieving agency within the constructs, dreams, and nightmares of a "Great Man's" mind.
Snow Crash - Neal Stephenson.
Gravity's Rainbow - Thomas Pynchon.
Dhalgren - Samuel L. "Chip" Delany.