Harry Potter and the Half-Blood Prince Study Guide

Some reviewers noted that Half-Blood Prince contained a darker tone than the previous Potter novels. The Christian Science Monitor 's reviewer Yvonne Zipp considered the first half to contain a lighter tone to soften the unhappy ending. The Boston Globe reviewer Liz Rosenberg wrote, "lightness [is] slimmer than ever in this darkening series...[there is] a new charge of gloom and darkness. I felt depressed by the time I was two-thirds of the way through". She also compared the setting to Charles Dickens's depictions of London, as it was "brooding, broken, gold-lit, as living character as any other". Christopher Paolini called the darker tone "disquieting" because it was so different from the earlier books. Liesl Schillinger, a contributor to The New York Times book review

, also noted that Half-Blood Prince was "far darker" but "leavened with humor, romance and snappy dialogue". She suggested a connection to the 11 September attacks, as the later, darker novels were written after that event. David Kipen, a critic of the San Francisco Chronicle considered the "darkness as a sign of our paranoid times" and singled out curfews and searches that were part of the tightened security at Hogwarts, as a resemblance to our world.

Julia Keller, a critic for the Chicago Tribune , highlighted the humour found in the novel and claimed it to be the success of the Harry Potter saga. She acknowledged that "the books are dark and scary in places" but "no darkness in Half-Blood Prince ...is so immense that it cannot be rescued by a snicker or a smirk." She considered that Rowling was suggesting that difficult times could be worked through with imagination, hope, and humour, and compared this concept to works such as Madeleine L'Engle's A Wrinkle in Time and Kenneth Grahame's The Wind in the Willows .

Rosenberg wrote that the two main themes of Half-Blood Prince were love and death and praised Rowling's "affirmation of their central position in human lives". She considered love to be represented in several forms: the love of parent to child, teacher to student, and the romances that developed between the characters. Zipp noted trust and redemption to be themes promising to continue in the final book, which she thought "would add a greater layer of nuance and complexity to some characters who could sorely use it." Deepti Hajela also pointed out Harry's character development, that he was "no longer a boy wizard; he's a young man, determined to seek out and face a young man's challenges". Paolini had similar views, claiming, "the children have changed...they act like real teenagers."