In Proust Was a Neuroscientist Jonah Lehrer spends ~250 pages setting up the argument that artists have incredibly valuable (but frequently unprovable, at least temporarily anyway) insight into human cognition. Then he blows it in the epilogue. It’s worth the read for the chapter on Cézanne alone.
Jonah Lehrer’s How We Decide is a dissection of the unconscious systems we use to make decisions. He takes us through the impossibly complex system of rewards that form our emotional decision making system and ultimately make us supremely efficient decision makers, even if it seems like we make bad decisions all the time. Awareness (I won’t say understanding) of these systems is incredibly enlightening for designers.