I keep reading many things about the genitive disappearing, and indeed it's not uncommon to see forms like
das Buch von meinem Bruder
whose correctness (or lack thereof) I haven't been able to determine (or does that have a meaning more along the lines of "the book my brother gave me", ie that came from (von) him?). Besides that, it is my understanding that, even when sticking to the genitive, there are often different forms that can be used; for the above example, I can think of
das Buch meines Bruders
meines Bruders Buch
Also, is it different when proper nouns are involved? That is, are all the following valid:
das Buch von Karl
das Buch Karls
Karls Buch
Thanks.