Well, it depends, actually.
Theodor Mommsen is really high mountain on the landscape of ancient historiography even now. I think, his "Roman history" is still very much into current process of research. I was trained in Russian late medieval history, but his texts were cornerstone of our seminars on Antiquity.
Of course, all of us know single work by Bjornstjerne Bjornson. It's anthem of his motherland, Norway.
And it's strange to me to see the name of Maurice Maeterlink on this list! He is really such obscure figure in Western world? Here his "Blue bird" was super popular in the early XXth century (it was staged by Stanislavsky, I suppose) and become kind of symbol during the Soviet. As a play for children, true, but still... it gave its name to early soviet candy:
Конфект «Синяя птица», Обертка, Москопищепромсоюз, Паров. кондит. ф-ка пром. кооп. т-ва «Красный Конфетчик»,Изображены девочка и мальчик, сидящие у клетки с птицей. Герои пьесы Мориса Метерлинка "Синяя птица",Промышленная графика, СССР, 1920-е гг.,Кондитерские изделия, Конфеты, Москва...
electro.nekrasovka.ru
P. S. And give the chance to Paul von Heyse. He is one of my personal favorites. His short stories are such cozy bidermeier trinkets!