Quem fez o livro pode ter senso de humor.
“Hasn’ — hasn’ anyone bin able ter open their books?” said Hagrid, looking crestfallen.
The class all shook their heads.
“Yeh’ve got ter stroke ‘em,” said Hagrid, as though this was the most obvious thing in the world. “Look —”
He took Hermione’s copy and ripped off the Spellotape that bound it. The book tried to bite, but Hagrid ran a giant forefinger down its spine, and the book shivered, and then fell open and lay quiet in his hand.
“Oh, how silly we’ve all been!” Malfoy sneered. “We should have stroked them! Why didn’t we guess!”
“I — I thought they were funny,” Hagrid said uncertainly to Hermione.
“Oh, tremendously funny!” said Malfoy. “Really witty, giving us books that try and rip our hands off!”
Harry Potter and the Prisoner of Azkaban, Chapter 16, Talons and Tea Leaves
Imagine ter um livro que você não pode abrir ou que você não pode ver.
“Stop it! Stop it!” cried the manager, poking the walking stick through the bars and knocking the books apart. “I’m never stocking them again, never! It’s been bedlam! I thought we’d seen the worst when we bought two hundred copies of the Invisible Book of Invisibility — cost a fortune, and we never found them... Well... is there anything else I can help you with?”
Harry Potter and the Prisoner of Azkaban, Chapter 4, The Leaky Cauldron
Parece que é uma prática usada para vender mais livros. Posso pensar nos seguintes fatores
- Aumenta a frescura do livro
- Torna o livro diferente de outros livros
- O livro pode ser usado como uma brincadeira