It's a deserved classic. Of course the research is a bit dated. Also, it's worth bearing in mind that Stefan Zweig wrote this between two world wars, the first of which had made him a committed pacifist. He'd grown up in pre WWI Austria when in school the Habsburgs could do no wrong, and had seen where that type of history lesson led to, so he's somewhat iconoclastic/Habsburg-critisizing in response to that. All this being said, he was a master of the biographie romancee, and also of the German language; of course I don't know how good the translation is but he was a bestselling author the whole world over in his day. He was also very musical - he wrote the libretto for a late Richard Strauss opera, and when it was produced for the first time in 1933, his name wasn't mentioned anywhere, because Zweig was Jewish, and Hitler had arrived.

(His day ended in exile, in Brazil during WWII, where he committed suicide, shortly after finishing his memoirs of his youth in pre-WWI Vienna, Die Welt von Gestern, "The World of Yesterday".)

My own first Zweig work was his Joseph Fouché biography, a great example of how you can write the biography of someone you despise and yet make it absolutely fascinating. Most of the other people he wrote about he liked, including MA,but Fouché, he was both revolted and fascinated by, and it shows.