It may seem like a waste of time to write about a 21st-century Marxist. Many people believe that Marxism is dead and gone and has been since the fall of Communism in eastern Europe and the Soviet Union. Indeed many others believed it was dead long before that – at least here in the West. Therefore any Marxists such people acknowledge to still exist are deemed to be the largely ineffectual and harmless members of what amounts to cults or sects.
Whatever the case, books by Marx are currently political best-sellers all over the place, including in Marx's country of birth, Germany.
If you believe that Marxism is a cult or religion (or as close to being a religion as it can possibly be without thereby being a literal religion), then of course Marxism is not dead. Essentially, Marxism is not based on truth or accuracy. It is based on various ideas or memes that seem to have a long shelf life and which still fire the spirits of many people in the West. (And not all those people are white, middle-class students!) These Marxist hopes and dreams are based on theories which don't really require either truth or accuracy in order to inspire and motivate people. They are, then, almost myths ( 'Sorelian myths').
In addition, because it was the case that no revolution was ever forthcoming in Europe and the United States, Leftists/Marxists, on the whole, stopped believing in the imminent possibility of a violent revolution – even though they still agitated for one. Consequently, many Leftists have taken the advice of the Italian Marxist, Antonio Gramsci (first offered in the early 1930s). He directed Marxists/Leftists/progressives to “take over the institutions” in order to create a new Marxist/Leftist “hegemony”. (The Frankfurt School and many other Marxist theorists offered similar proposals.)
When it comes to Slavoj Žižek himself: he both has his cake and eats it. That is, he still believes in violent revolution as well as in taking over various and many institutions. Currently Žižek is a senior researcher at the Institute for Sociology and Philosophy at the University of Ljubljana in Slovenia; the international director of the Birkbeck Institute for the Humanities (London); a professor of philosophy and psychoanalysis at the European Graduate School; and an Eminent Scholar at Kyung Hee University, South Korea.
I said that Marxism is not dead: it's certainly not the case that Žižek is dead. In fact he's been called the “Elvis of cultural theory”. The journal Foreign Policy listed him in its Top 100 Global Thinkers list in 2012. Žižek has also appeared in films and documentaries, including the 2005 film, Žižek! And it's even the case that there's a journal dedicated entirely to his work: the International Journal of Žižek Studies.