Thomas Suddendorf, The Gap: The Science of What Separates Us from Other Animals(New York: Basic Books, 2013). A comprehensive up-to-date summary of identifying the key elements of human cognitive uniqueness.
Christopher Boehm, Hierarchy in the Forest: The Evolution of Egalitarian Behavior(Cambridge, MA: Harvard University Press, 1999). A sophisticated and penetrating analysis of a key regarding intrinsic human nature: whether we are fundamentally power-seeking or egalitarian.
Merlin Donald, Origins of the Modern Mind: Three Stages in the Evolution of Culture and Cognition (Cambridge, MA: Harvard University Press, 1991). Highly recommended for its valuable analysis of the evolution of human cognition in three stages, introducing the concept of mimetic culture.
Michael Tomasello, The Cultural Origins of Human Cognition(Cambridge, MA: Harvard University Press, 2000). Recommended for its explanation of the role of culture in human evolution, and its identification of shared intentionality as a crucial uniquely human characteristic.
Terrence W. Deacon, The Symbolic Species: The Co-Evolution of Language and the Brain(New York: Norton, 1997). Highly recommended for its analysis of the central role of the prefrontal cortex in the evolution of human cognition and symbolic thought.