Basically I think she was irritated by reviewers who give away too many plot twists and turns when they review her books, to the point that it made reading the book unnecessary. It was a long article, and interesting, but made no mention of the current craze for non-professional reviewers to post their thoughts about books on Amazon.
Reading these thoughts can be entertaining, or heartbreaking. Sometimes I suspect people have dashed onto Amazon, clicked on a book title without actually reading the blurb or sampling the text, and several hours later wondered why they didn't enjoy the story. Their review naturally disses the book in question. After all, the book is to blame, isn't it?
At others it is hard not to notice that authors from the same publishing house review and praise each other's books. It's noticeable even among the hardbacks these days. If the gushing comments are genuine, that's fine, but sometimes that little gremlin of suspicion raises its head and says, rather like Mandy Rice Davies - 'Well, he would say that, wouldn't he? ' because we know the author knows fine well that they'll be due a good review in return.
Is either part of good bookselling?
Arifa Akbar's answer to Joanne makes interesting reading, too: here