Amazon is rubbish. They don't allow you to comment on a book if you haven't bought anything from them with the particular account you want to use to write a comment! They say that's to assure high standards of reviews! But please: I could buy loads of books from them and STILL write rubbish reviews. That's not a reason, come on!
Actually I wanted to be the first to comment on a book, saying what superficial rubbish it is, unworthy to be printed in the first place. But no: I'm not allowed to comment, making my sophisticated and very valid opinion known to the World.