Hilzoy asks:

What’s the (European) work that is most inexplicably not in print in an English translation?

Let’s substitute regrettably for inexplicably, since the reason is not inexplicable at all, and mention the novels and stories of Catholic, Conservative Werner Bergengruen (1892-1964), particularly his trilogy: Der letze Rittmeister (1952), Die Rittmeisterin (1954), and Die dritte Kranz (1962).

Only the first of the trilogy, published in England as The Last Captain of Horse — a Portrait of Chivalry (Thames & Hudson, 1953), and Der Grosstyrann und das Gericht (1935), published as A Matter of Conscience (Thames & Hudson, 1952), have ever been translated, and both are long out of print.