Having seen all the films and read all the books, i found this disappointing. It was quite dull and not very well informed. There were a few facts that were actually wrong, and vague mentions of people who were perhaps mentioned in background passing in the books. e.g. '*name* - student sorted into *house name*'
The other problem i found with this book is that all the information comes from the first three books.
People like 'Luna Lovegood' aren't mentioned, even in passing and random things such as sweets that can be bought at Honeydukes are. The time-turner input isn't much helpful either - 'Time-Turner - a necklace with a hourglass on it.' It doesn't describe what it does or how rare they are. I understand that this would be a spoiler for those who haven't seen the films or read the books, but surely anyone who buys the Encyclopedia would have done so?
It's well seen that this book doesn't go into detail about any characters and their parts in the Harry Potter series as you would expect an Encyclopedia to, when you see under 'Malfoy, Draco - Slytherin, student at Hogwarts'. I would have enjoyed an Encyclopedia that covers the main points of the Harry Potter books, e.g. 'Longbottom, Neville - whizz at Herbology, slightly lanky and clumsy, faithful Griffindor.' It's disappointing to find such a juicy character as Remus Lupin and find that all this book says is 'Lupin, Remus J. - Defense Against the Dark Arts teacher in Harry's third year'. It mentions nothing of him being a werewolf or of his friendship with Harry's father and godfather. The same goes for Harry Potter himself...his entry? - 'Potter, Harry - a young boy who unexpectedly finds himself at Hogwarts studying wizardry.'
Overall, as a massive fan of HP, whether in film or book, i found this so disappointing that after the first page i skimmed through the entries and found myself put off by the numerous '... sorted into an unknown house' and lack of detail about very strong, intricate characters. Not a book for the die hard fan.