Structure problems and positives in Deathly Hallows
1. We've been set up for Snape to play a significant role, but instead get vast exposition on an already-dead character.
My disappointment with DH began with the previous book; HBP displayed from the second chapter that Snape was loyal to the Order and playing a dangerous double agent game, and would soon be required to do a terrible thing to keep his cover or be killed himself. I was dumbfounded when this was treated like some great surprise at the end of the book; while it deserved to be one climactic moment of the book, the true climax should have been the revelation to Harry that Snape and Dumbledore had planned the deception together. If the reader was told this at the beginning of the book, Harry should also have been told it by the end of the book. Leaving Harry in ignorance is poor narrative structure; the tale cannot be left to dangle like that, incomplete, at the end of a book.
Given that this plotline turned out to be the most significant part of HBP, whetting our appetites with Snape going into deep cover, DH should have followed through. In HBP Snape went from "side character who's loathsome but interesting" to "the other hero of the story." Snape should have played a significant role in the structure of DH, but instead he all but disappeared until a few pages before his death. While there are moments where his influence is there--Gryffindor's sword in the pond--they are invisible until after Snape has died. Only then is his story told, in one massive chapter of exposition.
What do we get instead of Snape's presence? We get, to my disappointment, considerable exposition regarding the life of Dumbledore--Dumbledore, who is dead. Again, poor narrative structure. The controversy surrounding Dumbledore is unfolded for us after he is dead. Snape's backstory is only told after he is dead. We no longer have any stake in what this means to the future actions of these characters, to their interactions with our protagonist. How different this knowledge would have resounded with us had these characters still been alive when we learned this! How we would have imagined Harry confronting Dumbledore, how much hope we would have had for Snape's survival (and how much more devastating his death), had we only known these things first. They would have been active portions of the story structure instead of past-tense exposition.
2. A change from the expected story structure established through six books--and not a well-executed change, either.
DH also disappoints by abandoning the school year structure that books one through six follow. Because of this DH feels like a book from a different series. We are used to the Harry Potter series being a tale of student interactions, knowledge gained through classes and textbooks, and contrivances by our heroes that are used to get around the restrictions of school rules and the school year itself. The last book abandons that, and that violation of reader expectations should not be forgiven lightly. DH could be considered an alternate reality story of the Harry Potter series, where the characters are placed into a high-fantasy quest story. One can argue whether it is a good quest story or not; I do not feel it is that good of one, myself, what with the time wasted doing nothing in the forest, the "madcap hijinks" feel of the trio's escapades (too silly right when the books should be at their darkest and most serious), and the flimsy contrivance to set the final battle at Hogwarts. These leech a great deal of dignity from the book, even the moments that are meant to be somber, such as Dobby's death. But whether it is a good quest story or not, it is a deviation from the structure that the reader has been asked to expect and now does expect.
3. Lack of emotional engagement in Harry's romantic destiny.
Both HBP and DH disappointed me in the romantic plotline regarding Harry and Ginny by failing to show their connection and/or affection for each other; instead we were told Harry was struck by sudden jealous lust for her, and this is all we have to support the concept of these two having a lifelong love. They may be right for each other conceptually, but there's nothing to make the reader feel it.
A positive! How Harry has been set up both to die and to live.
Despite all these negatives, one element within DH--arguably the most important and central element--shines through as well-planned and well-executed. At the end of book four, GoF, we are given a hint of something significant in Dumbledore's "gleam of something like triumph" when he is told Voldemort used Harry's blood for the ritual. We don't know why. We're left to think about it all through books five and six. And when we get the payoff, it's big. Harry learns he holds a fragment of Voldemort's soul (hinted at when we first learn of Horcruxes), and must die for Voldemort to die. But he does not know until after his death that his blood in Voldemort's flesh maintains enough of a link to return Harry to life if he chooses. It's wonderful--the theme of the entire series is that some things are worse than death and many things are worth death and death should not be feared if it must be faced. Harry has been groomed by Dumbledore to go to his death willing and unflinching, and go he does. The theme of the books required that he do this at the end. Yet he is saved from death not by a cheap cheat in my opinion, but by an element that has been established from the first book and hinted at, in a clever yet still obscure manner, in the fourth. Harry both dies and lives within this tale, and while it might have been gutsy to leave him dead there's a narrative justice that he goes willingly to his death but is allowed a happy ending.