Simulacra and Simulation (Simulacres et Simulation in French), published in 1981, is a philosophical treatise by Jean Baudrillard.
The Matrix makes many connections to Simulacra and Simulation. Neo is seen with a copy of Simulacra and Simulation at the beginning of The Matrix. He uses the hollowed book as a hiding place for cash and his important computer files. Neo's hollowed copy of the book has the chapter "On Nihilism" in the middle, not at the end of the book, where it is in reality. Morpheus refers to the real world outside the Matrix as the "desert of the real", a reference to Baudrillard's work. In the original script, Morpheus specifically referred to Baudrillard's book, however, in an interview, Baudrillard said "The Matrix" has nothing to do with his work. 
The hacker Tiera in the comic "A Life Less Empty" is also seen to have a copy of the book (mistitled "Simulacra and Simulations") on her shelf along with three other titles: Memoreaze, Interfazed and Byte Me, with a copy of Hackers Bible lying on her chest of drawers.
Simulacra and Simulation is known for discussions of images and signs, and how they relate to our contemporary society, wherein we have replaced reality and meaning with symbols and signs; what we know as reality actually is a simulation of reality. The simulacra to which Baudrillard refers are the signs of culture and media that create the reality we perceive: a world saturated with imagery, infused with communications media, sound, and commercial advertising. These simulacra of the real surpass the real world and thus become hyperreal, a world that is more-real-than-real; presupposing and preceding the real. In this world apathy and melancholy permeate human perception and begin eroding Nietzsche's feeling of ressentiment.
A specific analogy that Baudrillard uses is a fable derived from the work of Jorge Luis Borges. In it, a great Empire created a map that was so detailed it was as large as the Empire itself. The actual map grew and decayed as the Empire itself conquered or lost territory. When the Empire crumbled, all that was left was the map. In Baudrillard's rendition, it is the map that we are living in, the simulation of reality, and it is reality that is crumbling away from disuse.
- Jean Baudrillard, Simulacra and Simulations
- Translation of the interview with Le Nouvel Observateur regarding Matrix
- Simulacra and Simulation: Baudrillard and the Matrix by Richard Hanley
- Baudrillard; Cultura, simulacro y régimen de mortandad en el Sistema de los objetos by Adolfo Vasquez Rocca PhD