Well, my favourite book so far is book 6 (even though Dumbledore dies ), cause we see everybody growing up... even Ron's more mature! And Harry's a bit calmer than in book 5 (he sometimes got on my nerves with his impulsiveness!). Apart from that, everything seems to fit... y'know, almost all the pieces of the huge puzzle HP is are on the table, and after reading the 6th book, there are many mysteries that come to an end.
Cons: I miss Sirius so much