I first read about Karl Popper in about 1979 or 1980. I read about him in this superb slim overview by Bryan Magee, which had been published in 1973 or 1974. The book was one of the volumes in the Fontana Modern Masters series. The cover art was part of a bigger concept - and the particular example on the Popper book was a kinetic painting by Oliver Bevan.
The book is still easy to get from Abe or eBay. The story behind the cover art is HERE.