This, it has to be said, is mostly due to Zack Snyder. I'd greatly enjoyed Snyder's work on Dawn of the Dead and, indeed, Watchmen (the greatest DC comic of them all).
However, as gifted as he is, his movies tend towards empty spectacle, to say the least (see, or rather don't see, Sucker Punch).
So the recent Superman and Batman franchises, as presided over by Snyder, have wildly missed the mark. But not this one. Which seems to me to be due to the involvement of Joss Whedon (of Buffy and the Avengers fame).
The reason Zack Snyder's work fails is because he has no gift for characterisation, or at least no interest in it. His stuff is cold.
With the result that his DC movies have been glum, joyless slug-fests. It doesn't matter how great your action sequences are if the audience isn't engaged with the characters. (Superman v Batman was a classic example of this.)
But when Joss Whedon enters the equation, all that changes. Whedon is all about characterisation, and fun. He brings warmth and humour.
Joss Whedon co-wrote the script for Justice League (with Chris Terrio, who won an Oscar for Argo). Whedon also did some of the directing on the movie (uncredited) after Zack Snyder suffered a terrible family tragedy.
The entwining of Joss Whedon and Zack Snyder's sensibilities is perfect. Whedon brings the characters to life so we care about them and their fate. So when Snyder mounts one of his action sequences they work. Indeed, they almost blow your head off.
Justice League's cast is well chosen. The divine Gal Gadot is back as Wonder Woman, and every time she smiles the screen lights up.
Jason Momoa (who played Conan in the recent big screen reboot and was Daenerys's barbarian squeeze on Game of Thrones) is effective as Aquaman — if ever there was a character who could have gone wrong, this was it. But he's successfully been reimagined for the big screen. (Although he gets teased a lot. "Do you really talk to fish?")
Indeed, more successfully reimagined than Cyborg. But even this dud of a character works here, thanks to the acting of Ray Fisher and the writing of Whedon and Terrio.
Ben Affleck as Batman and Henry Cavill as Superman are both back. And, for the first time, I like them. Jeremy Irons is outstandingly amusing as Alfred the Butler, who is dressed here as a particularly British kind of nerd.
And speaking of nerds, the Flash has joined the team as portrayed by Ezra Miller, who was the incredibly evil Kevin in We Need to Talk About Kevin — a role which could hardly be more different than this one. The characterisation of the Flash matches that of the popular TV series... he's a lovable geek.
In fact, the whole team is pretty lovable, including those who would normally just be grunting hunks. Thanks, I think, to Joss Whedon.
This movie isn't remotely in the league — no pun intended — of Wonder Woman. But it's way better than I anticipated; engrossing fun from start to finish, with some genuine thrills. If you like the DC universe, this may well be your cup of tea.
Oh... and I apologise for the "spoiler" that Superman is back in this movie. But you never really believed he was dead, did you?
(Image credits: Posters are legion at Imp Awards.)