In the introduction to our (soon to be released) edition of Stefan Zweig's Journey Into the Past, André Aciman remarks that "it is difficult to think of any European worthy of notice in the early decades of the past century whose biography would not at one point or another invoke the name of Stefan Zweig." And Zweig's own autobiography likewise references many notables. In the following, taken from the 1943 translation of Zweig's World of Yesterday, he talks about meeting, and working with, James Joyce:
When I became acquainted with James Joyce . . . he harshly rejected all association with England. He was Irish. True, he wrote in the English language but did not think in English and didn’t want to think in English. “I’d like a language,” he said, “which is above all languages, a language to which all will do service. I cannot express myself in English without enclosing myself in a tradition.” This was not quite clear to me; I did not know of his Ulysses, on which he was then working; he had merely lent me A Portrait of the Artist as a Young Man, his only copy, and his little drama Exiles which I had thought to translate in order to be of use to him. The better I knew him the more his incredible knowledge of languages astonished me; his round firmly sculptured brow, which shone smooth like porcelain in the electric light, stored every vocable of every idiom and he was brilliantly able to toss and keep them balanced in the air. Once when he asked how I would reproduce a difficult sentence in the Portrait of the Artist in German, we attempted it first in French and then in Italian; for every word he was prepared with four or five in each idiom, even those in dialect, and he knew their value and weight to the finest nuance.
Hard evidence of Zweig's literary fame can be found in the Stefan Zweig collection at SUNY Fredonia. Here you can peruse some 6,000 letters sent to Zweig from the likes of "Martin Buber, Albert Schweitzer, Richard Strauss, Rainer Maria Rilke, Luigi Pirandello, Jules Romains, Joseph Roth, Frans Masereel..." along with "a good sampling of" translations of his books, which were translated into 50-odd languages.
A sadder reminder of Zweig's notoriety is on view at an LA Times blog post of a few years back, which reproduces the front page of the paper from May 3rd, 1938. The article is headlined, "Austria Sees Nazi Fire of Jewish Books," and it tells of the burning of Zweig's works, along with works by other prominent writers.
Finally, it's worth reading Clive James's appraisal of Zweig, reproduced in Slate a few years back.