Roger, we all define the star system differently. For me, five stars does not mean that a book was perfect, but that I found it deeply satisfying and/or startlingly innovative in form and content. Four stars still means that it was a very enjoyable book. It partly depends on what the book sparks in me, and I cannot guarantee that that book will have the same effect on other readers. I try to define what my own tastes are and what I think is likely to appeal to other readers.