Irrational Man: A Study in Existential Philosophy

Irrational Man: A Study in Existential Philosophy by William Christopher Barrett (1913–92) introduced existentialism to the English speaking world. He defines terms & gives the background on philosophical terms & concepts, aiming at general readers.
The need for a native English speaker to write a text on existentialist philosophy was paramount for its understanding, since most primary philosophers in this movement weren't native English speakers. While Kierkegaard's works had been translated decades earlier, the full impact of existential philosophy hadn't yet been felt in the English speaking world when this book was produced. Being & Nothingness had been available in English for only a couple of years, Kaufmann's Thus Spoke Zarathustra translation had been out only a few more & Being & Time hadn't yet been translated.
In the four parts of the book, Barrett briefly explains the philosophical tradition to which existentialism reacted & then its main concepts.
Part 1: The Present Age--shows the impact that existentialism has had on culture even without being a widely known philosophical school of thought.
Part 2: Sources of Existentialism--traces the development of philosophy as it pertains to being, ontology & metaphysics. This serves to show the contrast between existentialist thought & other forms of philosophy.
Part 3: The Existentialists--Kierkegaard, Nietzsche, Heidegger & Sartre are introduced along with their thinking & terminology. The discussion of each serves as a map for those seeking entry into the primary works of each, which can be dense with unique terminology. The material in each section summarizes the main points each philosopher contributed to existentialism. The reaction of one philosopher to another is explored. The philosophers are also situated in the larger history of philosophical investigations outside of existentialism itself. Barrett concentrates on these main philosophers & avoids an in-depth discussion of other existentialist artists, writers etc.
Part 4: Integral vs Rational Man--applies existentialist thought to the world of the late 1950s, during the Cold War.
Appendix 1: "Negation, Finitude & the Nature of Man" '57 paper
Appendix 2: discusses existentialism & analytic philosophy.