Serious, Somber, Pensive
Harry Potter and the Deathly Hallows shows how very, very far J.K. Rowling's tone in these book has transformed from the original lighthearted romps of early books like Harry Potter and the Sorcerer's Stone or Harry Potter and the Chamber of Secrets. The truth is, it would be impossible to keep up the punny delight of those early books, given the weight of what's going on in this one – the seriousness of Harry's quest necessitates the seriousness of the tone. Harry's basically going through the biggest crisis of his life here, and the whole world is weighing upon his shoulders. So, of course, given that we pretty much see the world through Harry's experiences, our vision of it is a lot darker in this book than in the previous ones. We go through the same things Harry does, including his tormented decision to give himself over to death, which makes for a pretty quiet, thoughtful, and sometimes scary ride.