Sorting these covers by decade
The Once and Future King by decade
T. H. White
23 covers from 26 printings with a known year, 2010s back to 1930s
2010s
2 covers · 2 publishers, Klett-Cotta Verlag and Penguin Classics among them
2000s
5 covers · 5 publishers, sparknotes and Paw Prints 2008-06-26 among them
1990s
3 covers · 3 publishers, HarperCollins and Ace Books among them
1980s
3 covers · 2 of 5 printings say paperback · 3 publishers, Berkley and Demco Media among them
1970s
3 covers · 3 publishers, Book Club Associates and Berkley among them
1960s
3 covers · 3 publishers, Fontana and Collins, London among them
1950s
3 covers · 2 of 6 printings say paperback · 4 publishers, Putnam and Ace Books among them
1930s
1 cover · 1 publisher, G. P. Putnam's Sons
Covers from Open Library, each in the decade of the earliest printing that carries it. What the catalogues never scanned is missing here too. See the whole wall.