His work is multimedia-based, specializing in drawing, sculpture, live performance, animation and film; the majority of which addresses South Africa's history as regards the subjects of apartheid and colonialism. William and his work has been described thus:
[...]a remarkably versatile artist whose work combines the political with the poetic[...]his work is often imbued with dreamy, lyrical undertones or comedic bits of self-deprecation that render his powerful messages both alluring and ambivalent.
from Fortuna (2013)
William's work is currently in exhibition at The Broad art museum in Los Angeles, the installation is titled In Praise of Shadows, which will be running through April 9th of this year.
He was also profiled by The New Yorker in 2010, and it's a very insightful article regarding the history of his career and also his life, the variety of his work, and the various influences upon it.