Though my areas of specialization are French philosophy, political philosophy and ethics, Sartre has until recently been something of an embarassing omission for me. After a few attempts with his literary works in undergrad, I neglected his thought until relatively recently. Hanging out with Devin and reading his Sartre-related blog entries has lit a fire under me, and I'm finally discovering the joys of Sartre - specifically, and because this is where my interests lie, I've flirted with the early stuff but have begun to engage in earnest with the Sartre of the Critique of Dialectical Reason. Depending on how you roll, the Critique is either Sartre's greatest work, a timely contribution to the question of praxis; or, you might agree with Foucault, Althusser, and other contemporaries who read it as an anachronistic and arguably "tailist" theoretical statement (to use an awkward but favourite Lenin neologism). Right or wrong, my initial impression is that Sartre has produced an essential reading in 20th century political thought, and I should not have put off reading it for so long.
Now, because I'm trying to wrap up a PhD thesis this year, work on the later Sartre has been a low priority and therefore slow going. Which is why I have found Verso's (2008) edition of Between Existentialism and Marxism to be a great primer or entering wedge. The question of introductions has come up numerous times on this blog, and here I'll reiterate that a good introduction is worth its weight in gold. The book in question is a collection of interviews, talks and essays that try to bridge Sartre's autonomous/literary/existentialist projects and concerns to his more engaged, Marx-inspired side. It's commonly known that Sartre both wanted communist approval, but could never bring himself to join the party; that he called for political engagement from intellectuals, but devoted perhaps an inordinate amount of time to literary biographies and the like; that finally, his very conception of an intellectual was to become troubled. All of that is here, and one gets a good sense of how these concerns developed. For would-be readers of the Critique, it's also nice to see Sartre moving towards, and in the wake of, the language and concepts of that greater work. Perhaps the most interesting aspect of Between is the way in which Sartre, especially post-68, was able to articulate (but not solve!) some of the most important questions concerning spontaneity and party organization in late capitalism. As with any introduction, however, Between does not replace the work it introduces; ideally, it will help you get your bearings as regards the Critique. And once you've got a handle on that greater work, the introduction itself will likely appear to you in a new light.
If your curiosity has been piqued, I should mention that Verso's edition of the book is in the third set of their relatively affordable "Radical Thinkers" series. This is a good thing, if you're the consumer; by round three, Verso figured out how to make affordable books that don't fall apart in your hands on the first read.