I havent read the whole HP Series ever since following along when books 4, 5, 6 and 7 were released. That was some time ago!:-) 
 So it is really fun to revisit the world of wizards, Hogwarts and the fight against You-know-who. 
 I liked the Dobby story and Harrys kindness towards him. Also the introduction of Ginny as a minor character is vital for book 2.