Harry Potter and the Half-Blood Prince 

Is there really any reason to review a new Harry Potter movie? Fans of the series have already seen it in droves, then engaged in vociferous online and off-line dissections of the adaptation and the colorful characters and plot twists the filmmakers were forced to omit. Hogwarts haters (if there are any left) will stay home.

So I offer this assessment solely for those who are still on the fence, perhaps wondering whether to accompany a more avid friend. Viewers who’ve never read a word of J.K. Rowling’s best sellers may feel as if they’ve stumbled into the middle of a season of “As the Wizarding World Turns.” The script offers no primer on these characters and why they’re all petrified of a villain who appears only in flashbacks. But Muggles with some passing Potter familiarity will find that director David Yates and his actors and composer and production designers and set dressers offer enough craft (or magic?) to make the film exciting even to viewers who have little investment in the increasingly Byzantine story.

After plodding through about 30 pages of explanatory gabbing at the dénouement of Harry Potter and the Order of the Phoenix, I decided that Rowling’s saga loses its tension when Dumbledore pulls too many fricking strings. Like the greatest dad or grandpa ever (crossed with Gandalf), the elderly Hogwarts headmaster always seems to be there guiding young Harry’s progression into manhood, and many of the books’ “mysteries” evaporate as soon as he puts on his exposition hat. Is it necessary to mention that Michael Gambon, who plays him in the film, acts circles around Daniel Radcliffe as Harry? In fact, Gambon and Alan Rickman (as maybe-he’s-evil-maybe-he-isn’t Professor Snape) give so much Shakespearean verve to their relatively small roles that it often seems as if Harry is the Chosen One only because he matches the books’ core demographic.

The current installment opens with London in the grip of a new Blitz, courtesy of dark lord Voldemort and his Death Eaters. The Chosen One, meanwhile, is flirting with a waitress who doesn’t seem to notice that he looks 12. Dumbledore puts a stop to this and whisks Harry away to meet Horace Slughorn (Jim Broadbent), the new potions master, who could be hiding a vital piece of information about Voldemort’s youth. In potions class, Harry happens on an old textbook in which a former pupil — identified only as “the Half-Blood Prince” — has scribbled handy cheat sheets. Meanwhile, Draco Malfoy is up to something really not good that involves birds and a portable cabinet. (Tom Felton, who plays him, is starting to look and glower like Nicolas Cage.)

The film offers meanwhiles on meanwhiles, and that’s not even counting the various student love triangles and unrequited crushes. It wanders from plotline to plotline until, about 40 minutes from the end, everything comes together with a satisfying snap. When Yates slows down for a revealing fireside scene involving Slughorn and Hagrid (Robbie Coltrane), both actors pull out all the stops, and the movie achieves the grandeur of great adult drama.

That’s not to suggest children’s dramas are trivial. Some of the movie’s scenes have the oddness and beauty of the best fables, and the ending is as starkly distressing as it should be. Harry continues to be a frustratingly generic hero, and his more interesting friends Ron and Hermione don’t have much to do here beyond the aforementioned snogging. But Ginny Weasley (Bonnie Wright) has a gleam of mature wit in her eye that bodes well for the two planned sequels.

In my book, Harry Potter will never be up there with great literature or even children’s classics. But Rowling begs, borrows and steals enough from the long and rich tradition of British fantasy to make it work. And the film partakes of the equally long and rich tradition of British pantomime, in which thespians who could be doing Pinter choose instead to play characters with silly names and amuse themselves royally. Most of the audience will, too.