The Half Blood Prince is a hugely significant book in the
series, and whilst it is tempting to lament some things not given enough time or emphasis in the film as they are in the novel — like Greyback the vile werewolf, the abominable Bellatrix, old
stalwarts of the Order of the Phoenix and Ron's Quidditch insecurities (
although the main Quidditch scene is satisfying, particularly the final save by Ron)-- one must remember a conceptually vast 500 + page novel is being distilled into a two and a half hour film.