BY ROBERT EIDELBERG IN HIS UNIQUE SERIES OF INTERACTIVE BOOKS ON KNOWING AND THINKINGWE DON T KNOW: The Book of Non-Knowledge and the Volume of Our Current IgnoranceGOOD THINKING: A Self-Improvement Approach to Getting Your Mind to Go from Huh? to Hmm to Aha! PLAYING DETECTIVE: A Self-Improvement Approach to Becoming a More Mindful Thinker, Reader, and Writer by Solving MysteriesEVIDENTLY, MY DEAR ARMCHAIR DETECTIVE: Solving Ten Classic Mysteries Together With Their Celebrated Sleuths WHO S THERE? in Shakespeare s Hamlet That Is the Question!