When Joseph Beuys visited New York in the 1970s he renamed the twin towers of the World Trade Centre after the healing saints Cosmas and Damian, who, it is said, transplanted black limbs on to white patients and white limbs on to black. Beuys's postcard of the World Trade Centre, with the names Cosmas and Damian scribbled on the towers, sits among the other jokes, drawings and relics in this intimate encounter with the artist. It is a haunting instance of his ability to claim even the largest objects as Beuys sculptures, and to replace reality with his own, personal history of the world, as if everything he touched turned to felt.

Beuys gave Germany its imagination back. His drawings with their totemic figures, his ritualistic use of felt and fat, his monumental sculptures, such as Tramstop, assert the human need for myth and symbol. He showed how the worship of oaks was not Nazi but went back to Celtic prehistory. He valued tales of plurality, flow, democracy. Hence his fascination with Cosmas and Damian and their inter-racial surgery.

What does not always come across in Beuys's large sculptures is his humour. Bits and Pieces nicely leavens our sense of Beuys. There is a joyous poem-letter about his favourite foods, reminiscent of Günter Grass's novel The Flounder in its celebration of earthy pleasure. There are postcards made out of wood, and evidence of Beuys's fandom of the bank robber John Dillinger. Bits and Pieces is a loving archive of one of the 20th century's great artists, and we are lucky to have it.