I'm working my way through Slavoj Zizek's _The Parallax View_ right now, in part for work and in part for interest. Zizek's one of those thinkers who is more entertaining and provocative than he is substantive. There's a value in reading material that prods one to thinking in fresh ways, though. The trouble with Zizek's reasoning is that, for all his appeals to Hegel and Marx and Lukacs and dialectical thinking generally, he's forgotten the basics of deductive reasoning. For instance, he'll cite an example of how Jimmy Stewart passes gas in _Rear Window_, and declare that this tells us X about the structure of subjectivity... without any warrant or evidence. It might have worked as poetry but it does not as criticism or philosophy.
I bring it up because Zizek is one of the few contemporary social thinkers who has anything at all to say about globalized Buddhism, "Western Buddhism," and so on. Much of what he says about Buddhism as such is incoherent; if he'd read Trungpa on spiritual materialism and Nagarjuna (just to see what emptiness means and how a real dialectician works), his books would be a lot shorter.
There's another thing about Zizek. He's at his best (or at least his least obfuscated) when he's relying on the dialectical materialism of his youth, instead of the Lacanian patois he went to school for. That shit is opaque and not well reasoned. I'm unlikely to continue reading this book to the end, actually, because most of his relevant premises are worked out in advance by much earlier writers such as... Engels (Anti-Durhing) and Lenin (Criticism and Emperio-Criticism).
So, what's the value in reading this sort of material? I think it's useful to exercise the critical faculty. It's helpful to know what outsiders have to say about our practices as Buddhists, so we can interface better with the world at large and when appropriate reflect on the strengths and shortcomings of our practice.
You never really know until afterward who your friends are going to be, so you might as well have an open mind about it.