Everyone who purchases this book expecting it to be the long awaited next installment of the His Dark Materials story will probably be a bit disappointed. After all, it's only (only?) a short story about Lyra and Pan, while all the other great characters of the previous books are missing. Then again, I'd rather read a short story about a teenage Lyra while we're all waiting for the upcoming Book of Dust than simply go on Pullman withdrawal for who knows how long...
The book includes a map of Lyra's Oxford and (what I almost liked most about he book) a postcard of Oxford depicting among other things the famous park bench from The Amber Spyglass :-)
My final verdict is: don't expect too much (it's not at all as long as we are used to from the other books!) but try it anyway. If you are a fan of His Dark Materials, you are going to like it!