Hm, you are right. Those lists can't be perfect and giving this a second look, I guess my comment was hasty. For the choices I thought weird I can mostly see the justification when researching the titles a bit more (and partly by checking for their names in my language -> properly identifying them).

For what it's worth and what mostly triggered my comment, I expected 1984 to be on the list but thought it missing, but as mentioned in the other comments I was wrong about that, it's just listed with the numbers written out. Le petit prince I wouldn't have wanted on the list, I know it's popular and french, but I never got the appeal. Ulysses, as mentioned below, surprised me as I thought it's only popular in some countries, and regardless of that I think its just not readable. I would kick out two of the Lord of the ring books, one is enough and it's not like each of them had a different impact.

Maybe even more subjective, The Hound of the Baskervilles is important and well known and everything, but does it really held up when you read it today? If not, which would be my opinion, should it be on the list regardless? And I'd consider replacing Thomas Mann Zauberberg with Tod in Venedig, just because I liked it a lot.

For missing books: Louis Begley is an author I felt to be missing, probably with Wartime lies, or About Schmidt. The first Harry Potter as well, but I understand that in 1999 it was too early for that judgement. Stephenson's Snow Crash is missing, maybe replaceable with Neuromancer to have something of that genre. Talking german literature with Thomas Mann above, Alfred Andersch Die Rote would have a place on my personal list, as well as Die Wand by Marlen Haushofer. Haruki Murakami is missing, though maybe with 1Q84 he better fits into a list of the current century. Stephen King? Paul Auster? Philip Roth? Though maybe that would be for The Human Stain, and that's from 2000.

As an aside, I was happily surprised to see The Master and Margarita on the list. It's one of the more known books that I thought had a very special charm, but not one I'd expect to see working on many, as one would have to have read Goethe's Faust and liked it...