Interestingly, Riddle's Diary could be compared to Snape's Potions Book. Both were used by their respective owners as an outlet to use Dark Magic: Tom Riddle used his diary to create his first Horcrux, while Snape used his textbook to create original magic. Both books were used by other people without the knowledge of the owner's true identity until later. This further highlighted the personal similarities between Riddle and Snape. Whether this was intentional on Rowling's part or merely a coincidence was unknown. It was because of Ginny's experience with the diary that made her resent Harry's choice of following Snape's textbook instructions.