Lots of things moving really fast
I fell off of following comic book movies back around the second "original" Spider-man movie (back when Tobey Maguire was still doing the web-slinging). So jumping straight into a 2023 animated Spider-Man sequel set in the "Spider-verse" was kind of like, having not jogged for two decades, you one day decide you're going to do two hours of windsprints.
Across the Spider-verse fits within a broader vein of classic comic book heroes reformulated into new characters and reset within bigger, broader "meta" comic book universes. The movie's center of gravity is not one, but two, spider-bitten super-heroes: Gwen and Miles. They're fighting crime in New York and tackling the challenges of adolescence (Gwen as a Spider-Woman, Miles as a Spider-Man)--but here's the knot: they're from different New Yorks in different universes.
This, of course, is part of the central conceit of the "Metaverse," the notion du jeure that there are infinite parallel worlds and universes all running alongside each other simultaneously. As it happens, there is a common strand between a fairly large number of these parallel universes: they all have New York Cities. More than that, though, all these New York Cities have radioactive spiders biting teenagers and turning them into a wide variety of spider-themed super-heroes who feel compelled, despite the usual challenges of adolescence, to fight crime.
Gwen and Miles are two such kids, misunderstood by their parents and friends, who feel overwhelmed by the awesome power of being teenagers with superpowers. When a faceless, bumbling villain called "Spot" shows up in Miles' New York, throwing holes (that look an awful lot like rorschach tests) into reality hither and yon, Miles and Gwen come to learn about the Spider-verse. Turns out all these alternate universe spider-heroes have a central node, a big futuristic city, where they basically make sure all their respective threads run the way they're supposed to. That point's really important, apparently. So important, the idea takes on a term of truly breath-taking self-awareness--it's Canon. And as long as everyone in the Spider-verse follows the Canon, everything can go on, more or less smoothly.
Spot's quest for vengeance against Miles threatens to destroy the Spider-verse's Canon. While Miles' quest to chart his own destiny pretty much does the same. And, lo, lots of things move really fast and blow up.
This really isn't my kind of movie (we took our younger son to see it), but that's not a fair critique in a review, so I'll try to hit the highs and lows on the movie's own terms. In terms of animation, this was a beautiful movie. Computer-generated animation has come a long way, and Across the Spider-verse shows it at its best. The action--and there's ample plenty of it--is fluid, fast (and at times, at least for this old Gen-X'er, a little bit overwhelming). The backdrops were inspired, alternating between sweeping cityscapes and, at times, evocative color spreads. The latter could've come straight out of a Ralph Bakshi movie (and I mean that as high praise). The voice actors all put in solid performances, as well. The script-writers deserve praise for the dialogue, which differentiated characters' voices while avoiding info-dumps. The score wasn't bad if urban and techno beats are your thing.
The plot, however ... needed some tightening up. I say that recognizing this is comic book stuff, so its supposed to be big and sprawly and kind of winding. But still, the story line ran wild and never really cohered. It's also larded with teen angst. Everything in this movie--every parent, guardian, villain, and mentor, every secondary and tertiary character, heck, the whole "Spider-verse," becomes nothing but a crucible for Gwen and Miles' struggle of being misunderstood. That aspect of the characters certainly deserved a few beats in the story; it didn't deserve to be beaten to death.
But overall, I think, Across the Spider-verse is a solid contribution to the modern take on the classics. Whether it rises to Canon or not, I guess we'll have to wait for the next installment to find out...