Because one item is a book that almost anyone can afford to buy, suitable for all age groups... and the other is an electronic gadget that not all people can afford to buy.
To me, this is just more lazy journalism, identical to all the articles that starting appearing a couple of years ago using the word 'iPod' to stoke interest. Not relevant to the iPhone in the slightest.
And please address Harry Potter book-related discussion in one of these threads in the Community Forum. Thanks.
I believe this is supposed to be the last Harry Potter book. I think that might be the reason for a lot of the hype for it's release. Harry Potter fans are very anxious to learn if Harry dies or not. Personally I really don't really care.