His two-volume biography of Proust was published in 1959 and 1965. According to Miron Grindea, this was "rightly greeted as one of the great achievements in literary history", and it is still widely considered to be one of the finest literary biographies in the English language. Its second volume won the Duff Cooper Prize. His later work Chateaubriand: Volume 1 – The Longed-For Tempests was awarded the 1977 James Tait Black Memorial Prize.
Translations into German (1962 & 1968), Italian (1965), French (1966), Spanish (1967), and Polish (1972)
1965: The Vinland Map and the Tartar Relation (with R. A. Skelton and Thomas E. Marston). New Haven: Yale University Press. Painter contributed: The Tartar Relation, edited, with introduction, translation and commentary; The Tartar Relation and the Vinland Map: an interpretation (New ed. New Haven: Yale University Press, 1995. ISBN 0300065205)