Hilma af Klint: Tree of Knowledge[David Zwirner Books] The first detailed survey of Swedish artist Hilma af Klints groundbreaking Tree of Knowledge series Revelatory and sublime. . . . Her work remains conceptually open enough for viewers to draw their own conclusions, insert their own meaning and feel transported to other glorious worlds. The New York Times One of the most inventive artists of the twentieth century, af Klint was a pioneer of abstraction. Her first forays into