Looks like the third time’s the charm with the young-adult fantasy franchises. It wasn’t until “Prisoner of Azkaban” that the Harry Potter films really came into their own, and now “Eclipse” brings the “Twilight” series into the big leagues. It still isn’t great, and there still isn’t much crossover appeal, but it’s easily the best of the three films so far, with a well-constructed story, suitable climaxes, and — at last! — a main character who occasionally thinks for herself rather than being defined by her monster boyfriends. The men who are coerced into seeing “Eclipse” with their ladyfolk will surely enjoy this one more than the last two.

Our story begins with vampire fetishist Bella Swann (Kristen Stewart) about to finish high school. She hopes her undead boyfriend Edward (Robert Pattinson) will give her immortality as a graduation gift; Edward hopes he can convince Bella to marry him before he vampirizes her, as he is old-fashioned and courtly. Meanwhile, Native American werewolf Jacob (Taylor Lautner), the poor sap, still hopes Bella will forget the blood-sucker and choose him.

But there are larger issues to deal with. The problems of three little people, or one little person and two monsters, don’t amount to a hill of beans in this crazy world. In nearby Seattle, young people are going missing in large numbers, apparently being converted by a rogue vampire named Riley (Xavier Samuel), who’s assembling an army of reckless and especially bloodthirsty new recruits. Bella and company still have Victoria to worry about, too. She might have shapeshifted from Rachelle Lefevre into Bryce Dallas Howard (a lateral move at best), but her goal of killing Bella remains intact.

As you know, the vampires and the werewolves don’t cotton to each other. They cotton to a lot of things, but each other is not one of them. But when it’s discovered that Riley is stalking Bella for an unknown but surely nefarious purpose, the wolfmen and the draculas resolve to join forces to keep her safe. This means a temporary truce between Edward and Jacob and their respective teams.

Oh, and the Volturi, the supreme vampire council: They are also in this movie. One of them is still Dakota Fanning.

Once again adapted by Melissa Rosenberg from Stephenie Meyer’s novel, “Eclipse” was directed by David Slade, who made the energetically creepy vampire flick “30 Days of Night” a few years ago, as well as the unsettling “Hard Candy” (which, like “Twilight,” is about a teenage girl being stalked by a much-older man). He turns out to have been a good fit for the material. “Eclipse” is a little darker and more violent than its predecessors, and it has quite a bit less brooding and general mushiness (though still enough, I suspect, to satisfy fans of the books). The climactic battles, though brief, are respectably thrilling. For the first time, I’m interested in ancillary characters like Jasper (Jackson Rathbone) and Rosalie (Nikki Reed), whose pre-vampire backstories we learn here — and not just for kicks, either, as the new information we get on them figures into the current crisis.

Some of this newfound storytelling sophistication might be in the novel, too (I haven’t read it), but it’s Slade, Rosenberg, and the actors who make it work on the screen. Bella is still saddled with eye-rolling lines like “There’s nothing I’m ever going to want more than Edward,” and she still narrates the film only occasionally (a sign of lazy screenwriting) — but she also has believable conflicts and makes actual decisions, almost like a real grown up would. Stewart, Pattinson, and Lautner are all getting better as they get older, gradually giving their characters more nuance than they started with.

The final book in the series, “Breaking Dawn,” will be split into two films, with yet another director, Bill Condon, taking over. I hope he can build on Slade’s momentum and continue the franchise’s upward progression. If they keep improving like this, the people who automatically hate the films just because they’re popular with teenage girls will be forced to reconsider.

B (2 hrs., 4 min.; PG-13, a little mild sensuality, a lot of strong but bloodless violence.)