I would thoroughly recommend reading this book as a great way of improving your Spanish and having an unputdownable read at the same time. I was looking for something to read in Spanish, in order to improve my language skills, and, as I had loved all the Harry Potter films, but hadn't found time to read the books, I thought 'why not try to read Harry Potter in Spanish?'. I'm really glad I did! True, I need my big thick Spanish/English dictionary to hand to understand many of the words - but it does get easier the more you read, and my Spanish skills have improved noticeably since I've begun reading this book!
Thank you, J K Rowling, for a really enjoyable read - and for improving my Spanish!!!