I would have to mention several, and these just to provide a foundation from which to build:
(1) Mind and Nature, by Gregory Bateson
(2) On Meaning, by A.J. Greimas
(3) The Spell of the Sensuous, by David Abram
(4) The Chalice and the Blade, by Riane Eisler
(5) The Sex Contract, by Helen E. Fisher
(6) The Guru Papers, by Joel Kramer & Diana Alstad
(7) Buddhism Without Beliefs, by Stephen Batchelor
(8) The End of History and the Last Man, by Francis Fukuyama
(9) The Tao is Silent, by Raymond Smullyan
(10) Women, Fire and Dangerous things, by George Lakoff
(11) The Evolution of Cooperation, by Robert Axelrod
(12) The Adapted Mind, by Jerome H. Barkow, Leda Cosmides and
John Tooby
(13) Uniquely Human, by Philip Lieberman
(14) The Context of Self, by Richard M. Zaner
(15) The Human Use of Signs, by John Deely
(16) Experiencing and the Creation of Meaning, by Eugene Gendlin
(17) Social Cognition and the Acquisition of Self, by Michael Lewis
and Jeanne Brooks-Gunn
(18 & 19) The Field of Consciousness and Marginal Consciousness,
both by Aron Gurwitsch
(20 & 21) The Princioles of Genetic Epistemology and The
Equilibration of Cognitive Structures, both by Jean Piaget
(22) Making Silent Stones Speak, by Kathy D. Schick and Nicholas
Toth
(23) Tools, Language and Cognition in Human Evolution, edited by
Kathleen R. Gibson and Tim Ingold
(24) Investigations into the Origin of Language and Consciousness,
by Tran Duc Thao
(25) The Phenomenology of Perception, by Maurice Merleau-Ponty
(26) Being and Time, by Martin Heidegger
(27) The Crisis of European Sciences, by Edmund Husserl
(28) The Structure of Scientific Revolutions, by Thomas S. Kuhn
(29) The Laws of Form, by H. Spencer-Brown
(30) Chance and Chaos, by David Ruelle
(31) Biology as Ideology, by R.C.Lewontin
(32) Frontiers of Complexity, by Peter Coveny and Roger Highfield
(33) The Selfish Gene, by Richard Dawkins
(34 & 35) Consciousness Explained and Darwin's Dangerous Idea,
both by Daniel C. Dennett
(36 & 37) Psychosemantics and A Theory of Content and Other
Essays, both by Jerry A. Fodor
(38) Simulacra and Simulations, by Jean Baudrillard
(39) The Culture of the Copy, by Hillel Schwartz
(40) The Logic of Practice, by Pierre Bourdieu
(41) The Practice of Everyday Life, by Michel de Certeau
(42) What Computers (Still) Can't Do, by Hubert Dreyfus
Some are harder reading than others, but the issues they address
are both central and fundamental, two good indicators of
significance.