In no particular order:

* Siddhartha, Herman Hesse

* Man's Search for Meaning, Viktor Frankl

* The Obstacle is the Way, Ryan Holiday

* The Daily Stoic, Ryan Holiday

* The Effective Engineer, Edmund Lau

* The Lean Startup, Eric Ries

* The Personal MBA, Josh Kaufman

* Certain to Win, Chet Richards

* Left of Bang, Patrick Van Horn & Jason A. Riley

* Native Set Theory, Paul R. Halmos

EDIT: list formatting