With frank herbert's dune novels, I don't recommend the legends prequels or the sequels made by his son, brian herbert. They lack depth and seem hastily put together, and rely on too many deus ex machina.
I recommend from my childhood:
Zen and the Art of Motor Cycle Maintenance and Lila: An Enquiry Into Morals in that order, by Robert Pirsig.
Way of the Peaceful Warrior by Dan Millman.
The Prophet by Kahlil Gibran.
I also recommend:
Any Poetry by Rainer Maria Rilke.
Neuromancer by William Gibson.
The later works of Philip K Dick, after his schizophrenic breakdown began.
The Nights Dawn Trilogy and the Commonwealth Saga, by Peter F Hamilton.
Traces (short stories) by Stephen Baxter.
Violence: A Philosophy by Slavoj Zizek.
Ghost In The Shell (manga) by Shirow Masamune.
EDIT: I forgot to add:
Cultural Amnesia by Clive James. A particularly difficult read but extremely insightful and rewarding.
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Life is Painful. Suffering is Optional. Keep your face to the Sun and never see your Shadow.