Michael David Spivak is a mathematician specializing in differential geometry, an expositor of mathematics, and the founder of Publish-or-Perish Press. He is the author of the monumental five-volume Comprehensive Introduction to Differential Geometry. He received a Ph.D. from Princeton University under the supervision of John Milnor in 1964.
His book Calculus on Manifolds is widely admired. His unexcitingly and perhaps even misleadingly titled Calculus is not a mere calculus textbook - although it introduces calculus from first principles, it may be unsuitable for persons wishing to learn to apply calculus to scientific and engineering problems; it is primarily addressed to those who are attracted by the beauty of mathematics.
Spivak has also written Joy of Tex: A Gourmet Guide to Typesetting With the Ams-Tex Macro Package and The Hitchhiker's Guide to Calculus. The famous book Morse Theory, by John Milnor, was based on lecture notes by Spivak and Robert Wells. In each of his books he has hidden references to yellow pigs, an idea he apparently came up with at a bar while drinking with David C. Kelly. It is said that Michael Spivak now lives somewhere in Houston, Texas, for at least that's the address given for Publish or Perish, Inc, a firm he founded and has been using to promote mathematical education through the writing of textbooks.