* No Official Public Records: Publishers typically don't release specific sales figures for individual years, especially for books that were published earlier.
* Varying Release Dates: The book was released in the UK in 1997 and the US in 1998. Sales figures would vary depending on which region you're asking about.
* Ongoing Sales: The book continues to sell copies even decades after its initial release, making it difficult to isolate 1998 sales.
However, we do know that the book became incredibly popular very quickly. By the end of 1998, it was already a bestseller and gaining major momentum.