Set Theory: An Introduction to Independence Proofs is a textbook and reference work in set theory by Kenneth Kunen. It starts from basic notions, including the ZFC axioms, and quickly develops combinatorial notions such as trees, Suslin's problem, the diamond principle, and Martin's axiom. It develops some basic model theory (rather specifically aimed at models of set theory) and the theory of Gödel's constructible universe, L. The book then proceeds to describe the method of forcing. Kunen completely rewrote the book for the 2011 edition (under the title Set Theory), including more model theory.
References Baumgartner, James E. (June 1986). "Set Theory. An Introduction to Independence Proofs by Kenneth Kunen". The Journal of Symbolic Logic. 51 (2): 462–464. doi:10.2307/2274070. JSTOR 2274070. Henson, C. Ward (1984). "Set theory, An introduction to independence proofs by Kenneth Kunen". Bull. Amer. Math. Soc. 10: 129–131. doi:10.1090/S0273-0979-1984-15214-5. Kunen, Kenneth (1980). Set Theory: An Introduction to Independence Proofs. North-Holland. ISBN 0-444-85401-0. Zbl 0443.03021. Kunen, Kenneth (2011). Set theory. Studies in Logic. Vol. 34. London: College Publications. ISBN 978-1-84890-050-9. MR 2905394. Zbl 1262.03001.