It's the movie sequel to the Puella Magi Madoka Magica TV series. (Movies 1 and 2 are just compilations of the TV series with re-recorded voices and some new animation. Movie 1 does eps.1-8 and Movie 2 does eps.9-12. I think the latter's running time is actually longer than the corresponding episodes.)
This movie has been on my shelf since September, but it's taken me this long to make myself watch it. Madoka Magica isn't fun. It starts out cute and fluffy, but before long plunges into a zero-sum trip to hell in which there's no point in doing anything. Any good deeds you do will eventually be balanced out with the same amount of evil, at a massive human cost in suffering (to you). Gee. Sounds fun. What's more, the rules of this world are so surreal and arbitrary that it's hard to see any real-world meaning or significance. It's just Gen Urobuchi torturing his characters again.
In fairness the finale then turned that around and pulled a message of hope from its despair, but even so I was hardly queueing up for more.
However I always intended to watch this eventually. Madoka Magica is an important anime that's had a huge impact on many people. It has great emotional force. It's a rich text that can be studied and almost endlessly rewatched. As for this specific movie, it did extraordinary business for a late-night anime and I believe it's still the all-time highest grossing magical girl film.
In the end, I thought it was okay. I have no objection whatsoever to the cast, but I'm still not engaging with them as fully as the show's (many) fans clearly do. Urobuchi's plotting's still driven by his themes and ideas rather than his characters, I think. My reactions tend to be something like "aha, that's clever" on working out what's going on. Giving credit where it's due, though, Urobuchi's managed to write a satisfying sequel to an original work that at first glance looked sequel-proof. It's pleasing to think through its logic. It's dark (obviously) and has an ending that reflects that of the TV series while being more challenging to process. It's spikier, but doesn't feel like a betrayal of it. (Mind you, the credits roll just when you're expecting the film to continue for another half-hour. My reaction was, "What? THAT'S the end??")
The plot structure as a whole is a lot like the TV series, in fact, but doing Paradise Lost rather than Faust.
Don't even consider watching this film as your first Madoka Magica. Just don't. You'll sink without trace. You won't understand a thing. The two compilation films are highly regarded and will tell you everything you need to know, though, if you're tempted but prefer films to TV.
I do love the surreal visuals, though. It's Studio Shaft, as ever going beyond the call of sanity. It's beautiful. It's mind-expanding. It includes animated collage and mixed media, or at least that's what it looks like. In place it's also, apparently, a tribute to the 1983 George Lucas produced cut out animation film "Twice Upon a Time".
Interesting fact: this movie was submitted for the Best Animated Feature Oscar. It didn't reach the last five, although in fairness another anime film did (Studio Ghibli's The Wind Rises).
Is it a happy ending to the series? Yes, but only if you watch only the first twenty minutes. (Madoka Magica and happiness aren't things that go together.) It's impossible to discuss the ending in a spoiler-free review, but I think it's quite interesting and there's a lot of room for discussion on exactly what it means. It's deconstructing genre tropes (e.g. the Power of Love) in ways that sometimes go beyond even the TV series, not to mention tearing down fan expectations. It also does have emotion and powerful developments with Homura. I admire it. I just didn't connect with it, personally, as much as many people did.