i didn't like book 5 so much. first because...well because sirius died. i really like him. that is why book 3 is my favorite one.

then i really hated the way harry acted. he seemd to have become stupid all of a sudden. i hated him almost all along the book. and in the end i actually blamed him for sirius's death.

though i kinda liked the way umbridge gets it in the end from everybody. peeves, fred and george, and even mcgonagal turns against her. she was definitly a nice bad charachter (i mean she was a good choice for a bad charachter. she's really nasty).
though the book i liked the less was not OoTP but GoF. I don't know why but i felt so dissapointed at the end of that book...i just can't explain it
but jkr definitlly made it back with hbp... i really enjoyed this one. and i found it welcome after GoF and OoTP. because liking PoA so much i just expected better and better books to come next.