First read it in the 8th grade when I -like almost every teenager in the world- gobbled up anything Harry Potter-related. It's kind of sad that I don't own this book because: 
 1. It was way too thin and too expensive for my allowance back then. Sure the money would went to charity and everything BUT I JUST DON'T HAVE ENOUGH MONEY RIGHT NOW, OKAY? 
 2. Why save up buy it separately when there will be a BOX SET released after the series end? If I bought it then, I would lament the money I spent because I would want the box set too...(Haven't bought the box set either, in case someone would give it to me as a birthday present...I wish) 
 Now that there will be a new Harry Potter movie (series?), I think it's sort of an obligation to storm off to the nearest bookstore and buy this book (along with the box set) right away. After I graduate, I mean... 
 After reading... 
 Oh, the comments! Especially Ron's I love that boy's sense of humor. Really, I do. 
 I appreciate J.K> Rowling's effort in world-building. Her imagination is really great! There are many footnotes referencing to other wizarding books, this makes me hope J.K. Rowling would write those too. I especially want to read 'Hairy Snout, Human Heart', since Professor Lupin is my favourite Hogwarts teacher. 
 This book is truly a treasure for every Harry Potter's fan!