Compared to my natural language (Portuguese) it is very strange to use apostrophes to denote ownership, like:
Peter's book.
In Portuguese, I would say "the book of Peter".
Also, “inversions” like Peter girlfriend mother friend (I am not even sure how to write it), if every subject in this phrase owns something, it would be "Peter's girlfriend's mother's friend" that I know is wrong but at least would follow common sense. In Portuguese, I would have to say it like "the friend of the mother of Peter girlfriend".
Is there a rule of thumb that can be used, at least for the first case?
Peter's book
That tells me it is better to use the apostrophe version instead of the "of" version?
My main problem is when you are dealing with things that are not objects. A book is an object, but what about feelings like "Peter's feelings" or character traits "Peter's shyness" and other things that are not palpable things?
Is there a case where not using the apostrophe version is incorrect or weird?