I find it hard to say something good about this book, so here it goes: The word choice seemed to be slightly better than in the predecessor.
On the other part I believe you have to look at the whole series and I find there is no consistency: The first four books introduce a certain style: The reader learns only what Harry directly experiences. Characters are built up until the sixth book (e.g. infallibility of Hermione): The seventh goes against these characters. There are also psychological and physiological inconsistencies in the adolescence of the teenagers. None of the boys have mutation. It also seems absurd to assume that Harry’s wild year – his puberty – changes so abruptly.
Now for the actual seventh book: The first chapter is bad for reasons stated above, but what’s worse: The epilogue is even worse. It showes no imagination and is to sugar coated. There is no thread throughout the book you can follow no suspense, although you know they have to find the Horocruxes and destroy them, but you already know thy succeed. For the first good chapter you have to fight through 18 bad. In the nineteenth there is some mysteries, some magic. For the next good one you have to wait again. And after that the story is a failure. I surmised that in the some remaining chapters three Horocruxes must be found and destroyed and Voldemort must be killed. To achieve this several ‚Deus ex machina‘ must be introduced that just are not magical. Further more there is no suspense although several people die none of the death is emotionally as distressful as Dumbledors and his was already much less so than Sirus‘.
Conclusion: Instead of holding onto some conceptual consistency (36 Chapters) the story should be better worked out. The publication at this time seems to me overhasty.