Abelian categories: an introduction to the theory of functors
by Peter Freyd, 1964, 192 pages, PDF
Abstract and Concrete Categories: The Joy of Cats
by Jiri Adamek, Horst Herrlich, George Strecker, 1990, 496 pages, 4.2MB, PDF
Banach Modules and Functors on Categories of Banach Spaces
by J. Cigler, V. Losert, P.W. Michor, 1979, 297 pp, 15 MB, PDF
Basic Category Theory
by Jaap van Oosten, 2007, 88 pages, 500KB, PDF
Basic Category Theory
by Tom Leinster, 2016, 191 pp, 1.3MB, PDF
Basic Concepts of Enriched Category Theory
by Max Kelly, 2005, 143 pages, 0.9MB, PDF
Categorical Homotopy Theory
by Emily Riehl, 2014, 292 pp, 1.4MB, PDF
Categories and Homological Algebra
by Pierre Schapira, 2011, 125 pp, 630KB, PDF
Categories and Modules
by Takahiro Kato, 2015, 323 pp, 2MB, PDF
Categories, Types, and Structures
by Andrea Asperti and Giuseppe Longo, 1991, 300 pages, PDF
Category Theory
Stanford Encyclopedia of Philosophy, 2007
Category Theory
Wikibooks, 2010
Category Theory: A Gentle Introduction
by Peter Smith, 2016, 283 pp, 1.4MB, PDF
Category Theory and Functional Programming
by Mikael Vejdemo-Johansson, 2012, 99 pp, 410KB, PDF
Category Theory for Computing Science
by Michael Barr, Charles Wells, 1998, 544 pp, 2.1MB, PDF
Category Theory for Programmers
by Bartosz Milewski, 2017, 510 pp, 12MB, PDF
Category Theory for Scientists
by David I. Spivak, 2013, 261 pp, 4.7MB, PDF
Category Theory for the Sciences
by David I. Spivak, 2014, 496 pp, online html
Category Theory in Context
by Emily Riehl, 2016, 258 pp, 1.3MB, PDF
Category Theory Lecture Notes
by Daniele Turi, 2001, 61 pages, 540KB, PDF
Category Theory Lecture Notes
by Michael Barr, Charles Wells, 1999, 133 pages, 1.2MB, PDF
Coherence in Linear Predicate Logic
by K. Dosen, Z. Petric, 2010, 51 pages, 410KB, PDF
Combinatorics and Algebra of Tensor Calculus
by Sen Hu, Xuexing Lu, Yu Ye, 2015, 88 pp, 860KB, PDF
Computational Category Theory
by D.E. Rydeheard and R.M. Burstall, 2001, 263 pages, 0.9MB, PDF
Dynamical Systems and Sheaves
by D. I. Spivak, C. Vasilakopoulou, P. Schultz, 2016, 65 pp, 610KB, PDF
Functors and Categories of Banach Spaces
by Peter W. Michor, 1978, 103 pp, 4.7MB, PDF
A Gentle Introduction to Category Theory: the calculational approach
by Maarten M. Fokkinga, 1994, 80 pages, 390KB, PDF
Higher Algebra
by Jacob Lurie , 2011, 950 pp, 4.8MB, PDF
Higher-Dimensional Categories: an illustrated guide book
by Eugenia Cheng, Aaron Lauda, 2004, 1.7MB, PDF
Higher Operads, Higher Categories
by Tom Leinster, 2003, 410 pages, 3MB, PDF
Higher Topos Theory
by Jacob Lurie, 2009, 943 pp, 3.9MB, PDF
Homotopy Theories and Model Categories
by W. G. Dwyer, J. Spalinski, 1995, 56 pages, 420KB, PDF
Introducing categories to the practicing physicist
by Bob Coecke, 2008, 30 pages, 280KB, PDF
Introduction to Categories and Categorical Logic
by Samson Abramsky, Nikos Tzevelekos, 2011, 101 pages, 710KB, PDF
An Introduction to Category Theory in Four Easy Movements
by A. Schalk, H. Simmons, 2005, 197 pages, 1.2MB, PDF
An Invitation to General Algebra and Universal Constructions
by George M. Bergman, 1998, 398 pages, PS
Lectures on Tensor Categories and Modular Functors
by Bojko Bakalov, Alexander Kirillov, 2000, PS
Metric spaces, generalized logic and closed categories
by F. W. Lawvere, 2002, 37 pages, 2.8MB, PDF
Model Categories and Simplicial Methods
by Paul Goerss, Kristen Schemmerhorn, 2004, 46 pages, 410KB, PDF
Notes on Categories and Groupoids
by P. J. Higgins, 1971, 195 pages, 14MB, PDF
Practical Foundations of Mathematics
by Paul Taylor, 1999
Seminar on Triples and Categorical Homology Theory
by B. Eckmann, 1969, 304 pages, PDF, PS, DVI
Seven Sketches in Compositionality: An Invitation to Applied Category Theory
by Brendan Fong, David I Spivak, 2018, 243 pp, 2.1MB, PDF
Tensor Categories
by P. Etingof, S. Gelaki, D. Nikshych, and V. Ostrik, 2009, 540KB, PDF
Toposes, Triples and Theories
by Michael Barr, Charles Wells, 2005, 303 pages, 1.3MB, PDF