Umm - I wouldn't buy it from a seller that has it listed as edited by J K Rowling (who would have been 14 at the time...)
The editor was Robert Holdstock, who later wrote Mythago Wood..
If you click on the link for all 16 copies of the book you'll see all others are for Holdstock - I'm assuming the Rowling is a bookseller in a hurry doing their listings and forgetting to delete the field.