After living through a decade or so of superhero epics, I’m starting to feel a bit fatigued by the whole thing: Christopher Nolan’s Batman trilogy is done, Sam Raimi’s Spider-Man series was unceremoniously truncated, and the prospect of additional Wolverine-centric X-Men films is looking a bit dim. That said, last summer marked the release of my favorite Marvel film to date – “Guardians of the Galaxy” – so clearly there’s still some gas in the tank. But all in all, it’s fair to say I approached “Avengers: Age of Ultron” with a certain sense of obligation (certainly I haven’t been as jazzed about it as I am about next month’s “Jurassic World”).

I got something I did not expect.

“Age of Ultron” represents both a zenith and a nadir of the Marvel film enterprise. On one hand, the basic plot is atrocious – incoherent, divorced from the franchise’s meta-framework, and riddled with holes. In short, it’s cringe-inducingly bad (bad for a summer action blockbuster, which is saying a lot). On the other hand, it contains the most emotionally evocative scenes in any Marvel movie to date, a slew of richly textured characters whose interplay is a joy to watch, and breathtaking action setpieces.

The plot is extraordinarily simple, despite constant attempts by the writing staff (who clearly had Marvel studio execs over their shoulder the entire time) to muddy the waters. Tony Stark/Iron Man (Robert Downey Jr.) decides on a whim to design an artificial intelligence (the eponymous “Ultron” – voiced by a smirking James Spader) that will establish global peace. It goes haywire and becomes omnicidal. The Avengers try to kill it.

First off, there’s no coherent explanation for how Stark transformed from libertarian hero into totalitarian central planner. This is handwaved away with some statement to the effect of “well, the extraterrestrial invaders we faced last time were really scary.” Second, artificial intelligence makes for a fascinating plot device, but here, Ultron is basically just a human personality. He has human emotions and human vulnerabilities, but just happens to be plugged into a robot body. Creating a villain and slapping an “AI” label on it is conceptually bankrupt: even the aging “Terminator” franchise grasped long ago the titanic implications of a worldwide AI “singularity” emerging. Reference are made to Ultron “fleeing” and “hiding”…but this makes no sense at all. An AI of Ultron’s power would be ubiquitous – present in every Internet-connected device simultaneously, bending the entire global infrastructure to its will. That would be a legitimately compelling opponent for the Avengers – more accustomed to brute force than technological warfare – to face…but this Ultron just rants about evolution and extinction and judgment without any cogent rationale. Also, the metal comprising Captain America’s (Chris Evans) shield can bond with human organic tissue. Just because. Oh, and romance is apparently flowering between Black Widow (Scarlett Johansson) and Bruce Banner/Hulk (Mark Ruffalo). Don’t ask why, because it’s never explained. Finally, this is a movie in which the entire Internet – all of it – is run from a data clearinghouse in Sweden called the “Nexus.”

It goes on and on and on.

If that was where things ended, I would have been one seriously unhappy customer. But unexpectedly, “Age of Ultron” hits highs that match its lows.

Somehow, impossibly, director Joss Whedon manages to juggle an ever-expanding cast of characters with remarkable finesse. There are a couple new additions this time around – speedy Quicksilver and mind-altering Scarlet Witch (who have the charisma of potatoes, yet get inexplicably large amounts of screen time). The core sextet – Hulk, Captain America, Iron Man, Thor (Chris Hemsworth), Black Widow, and Hawkeye (Jeremy Renner) – is still dynamite, though, and each character gets plenty of individual attention.

By far the movie’s best moments are its quietest, when its protagonists can simply interact and reflect on life, love, and existence. At this point, audiences are emotionally invested in seeing what happens to this team: Whedon takes the time to explore deeply personal vulnerabilities, relationships, and dreams, venturing into previously uncharted territory for this superhero series. It seems banal to describe a summer movie like this as “emotionally affecting,” but there’s a deep warmth to many of these moments that transcends anything found in previous Marvel flicks.

And as to the action…I keep thinking I’m going to be underwhelmed by a tentpole-film climax one of these days, but Whedon somehow manages to amp up both the stakes and the mayhem this time around (if you thought there was some spectacular destruction in “Man of Steel,” you ain’t seen nothing yet). The “Hulk Buster” scene, featured in many of the promotional materials, is also a highlight. For all its plot problems, at its core “Age of Ultron” is a heaping helping of delirious geeky joy, and remains compulsively watchable throughout its considerable length.

As an additional aside, it’s worth mentioning that the soundtrack here is much better than its predecessor’s forgettable score. I attribute this primarily to the involvement of Danny Elfman – composer of the genuinely definitive Batman theme (sorry, Hans Zimmer).

When all’s said and done, “Age of Ultron” is worth your time and money (I saw it in 3D, which I highly recommend). The dork inside me acknowledges that where storyline convergence is concerned, this saga might be past the point of no return. But man oh man, if at some point I get to watch these guys slugging it out alongside Spider-Man and Wolverine and Daredevil, who cares?

I’ll continue to decry the fact that superhero movies are continuing to proliferate seemingly without end…but I’ll keep watching, and you probably will too.

VERDICT: 7.5/10 The Marvel Cinematic Universe is showing its cracks, but simultaneously breaking new thematic ground. Worth seeing.