Saunders MacLane, born in Connecticut in 1909, studied mathematics at Yale, Chicago and Göttingen and has taught mathematics at Harvard, Cornell and the University of Chicago. He is now the Max Mason Distinguished Service Professor of Mathematics at the University of Chicago. With Samuel Eilenberg he discovered the theory of categories and some of the basic ideas of homological algebra. His book Homology, covering the latter subject, was published by Springer-Verlag in 1963. This book summarizes the ideas and methods of category theory, which can now be effectively used by mathematicians working in a variety of other fields of mathematical research. The book is based on his lectures at Chicago, Canberra, Bowdoin and Tulane.
From the reviews of the second edition:
“The book under review is an introduction to the theory of categories which, as the title suggests, is addressed to the (no-nonsense) working mathematician, thus presenting the ideas and concepts of Category Theory in a broad context of mainstream examples (primarily from algebra). ... the book remains an authoritative source on the foundations of the theory and an accessible first introduction to categories. ... It is very well-written, with plenty of interesting discussions and stimulating exercises.” (Ittay Weiss, MAA Reviews, July, 2014)
Second Edition
S.M. Lane
Categories for the Working Mathematician
"A very useful introduction to category theory."―INTERNATIONALE MATHEMATISCHE NACHRICHTEN