books/reviews changes

README.md

@@ -31,16 +31,19 @@ erDiagram
     BOOK {
         string isbn PK
         string title
+        date publication_date
+        string author
     }
     REVIEW }o--|| BOOK : review_of
     REVIEW }o--|| USER : review_by
     REVIEW {
         uuid id PK
+        string isbn PK, FK
+        uuid user_id PK, FK
         bool read
         int rating
         string notes
-        string book_isbn PK, FK
-        string user_id PK, FK
+        string tags
     }
     PHYSICAL_BOOK }o--|| BOOK : is_a
     PHYSICAL_BOOK {