After a career of abstract expressionism (and protesting pop art), Guston underwent a crisis in the mid-1960s. Saying, for instance, “I like old-fashioned things like gravity”, Guston began to paint objects in the world around him. This was not, however, a return from the abstract to the concrete so much as a view of the concrete through eyes of abstraction. Some of his earliest paintings in this phase—just a few black brushstrokes on white paper, really—are stunning, such as 1967's Air or Wave II, which is simply an overlapping cascade running eccentrically down the paper. The books he paints become indistinguishable from skyscrapers, gravitas united with gravity.
Then, in 1970s, he finally cuts loose. A flood of drawings, first of caricatured Klansmen and then of boots and books and cobwebs and cherries and the rest of the trash of existence, give his work both a comic-like absurdity and a weight and feeling of urgency as he rushes to pump out his emotions. Some of his most wonderful, color drawings were executed in the very year of his death.
It would be pat to say Guston balanced the literal and the metaphorical, the abstract and the concrete, with ease—pat, and wrong. Instead he struggled with them, and put his struggles on paper. Thus on the one hand he was able to say,
The visible world, I think, is abstract and mysterious enough... Also there was a desire, a powerful desire though an impossibility, to paint things as if one had never seen them before, as if one had come from another planet.
like he painted his books. But he also arrested himself from returning to his earlier phase as an architecture astronaut:
Sometimes when my painting is becoming too artistic, I'll say to myself, ‘What if the shoe salesman asked you to paint a shoe on his window?’
If the salesman had asked, he would have received a cartoon showing the metaphorical weight of the world being fitted to a size 9.