Paul Strathern ably shifts from descriptions of the open relationship between Sartre and Simone de Beauvoir to analyses of the contributions of Heidegger and Kierkegaard to Sartre's belief that life is what you make it.
The jokes tend to be cynical and snarky in tone; after the publication of Being and Nothingness, for example, "word soon began to spread from the few who actually read the book to those who wished to talk about it as if they had."
The philosophical exegesis, however, is spot on, the equivalent of a very good college lecture by an instructor who genuinely wants to make sure students understand the material.
If you're at all interested in Sartre and existentialism, pick this book up for a quick, painless introduction.