About Scholastic Software and Intenet Group
This question shows up so much on my search query page, I figured I could help out: if you really want to reach an author, the standard practice is to send it to them, in care of their publisher.
So you could try:
J K Rowling
c/o Scholastic Books
557 Broadway
New York, New York 10012
And make sure you include a stamped, self-addressed envelope (ask about International Reply Coupons at the Post Office, unless you live within the same postal service area as she does): she may be a billionaire, but you don’t want her fumbling for stamps, do you? She’s got two more books to write . . . .