I bought this for my younger brother (who's been sick all week) yesterday! I already read it over the summer after Amazon bought the handwritten and jewel-encrusted original from J.K. Rowling and put each page up on their site, but I still read a couple pages on the train ride home.This version has an intro and footnotes as well as Prof. Dumbledore's commentaries at the end of each story. So even if you read it online, be sure to grab a copy to read the added info.
Image: amazon.com