My copy is a 1964 First Printing by Random House, hardcover, found at an art studio potlatch in Seattle. I've chosen to read only selected passages, as this is a fairly comprehensive text intended for reference.
The passages by Jean-Paul Sartre are worth slogging through for the gems amid the verbiage, but the most readable and enlightening passages are those of Soren Kierkegaard. Purely based on familiarity with their names, I read passages from Pascal, Marx, Herman Melville, Dostoevsky, Nietzsche, Sartre, Heidegger, Kierkegaard, Rainer Maria Rilke, and Kafka. The selections chosen to represent the forerunners of Existentialism were well-rounded, short, and to the point, for the most part: a good introduction. I studied English, not philosophy, so I found the more poetic passages, such as Rilke's letters, more enjoyable than the the abstract philosophical double-speak of Heidegger, Nietzsche, and others. The section relating existentialism to psychology was more down to earth by comparison. Though this text is a bit much for the lay person to get through, I found it valuable in terms of gaining an understanding of the 20th Century zeitgeist that led us, as society, to where we are today. Though many of us may not be able to quote the official definition of existentialism, we live in an age rife with existential crisis.