If J K Rowling had drawn this book to its conclusion three-quarters of the way through, when the appalling Dolores Ombrage gets her come-uppance at the hands of the Weasley twins, it would deserve seven stars.
The author is at her best when she allows her humour free reign, and a lot of HP no 5 is very funny indeed. Personally I found climax no 2, the long-drawn-out battle between Harry and Co and the Mangemorts, rather tedious stuff - almost as tedious as a description of a Quidditch match.
In particular I wish we didn't read on every other page that Harry is trembling with fear, or that Hermione appears terrified. It tends to diminish rather than add to the excitement. Just stop eating all those sweets, Harry, and you'll feel a lot calmer.