It's lovely. It's a light, happy Ghibli film that reminded me slightly of Alice in Wonderland. It's not by Hayao Miyazaki and it's a good deal less heavyweight than the films he was making around then, but I don't think that's a bad thing at all. I enjoyed it a lot.
It's a fantasy, but it starts in the real world and it has charmingly elegant transitions between reality and fantasy. Haru is a schoolgirl. She's bad at getting up on time and she used to claim to be able to talk to cats. One day she helps a cat on a busy road and things get ever more fantastical from there.
There's the Cat Kingdom, who will be enormously grateful in ways that could complicate your life. There are also some completely different cats with nothing at all to do with the Kingdom, of whom one is cool and taciturn (the Baron) and the other is huge, obese, rude and badly behaved (Muta). Watching Muta make trouble is one of this film's joys. The story starts out completely real with only the most delicate touches of fantasy, but then it keeps leading Haru deeper and deeper into impossibilities. She has to explain that she doesn't eat mice. She gets smaller, like Alice. (Some of the imagery of a big Haru in a little house is particularly Carrollian.) She encounters an eccentric royal court, like that of the Red Queen or the Queen of Hearts.
It's an unusual kind of sequel to Whispers of the Heart. (In that film, the Baron is a fictional character and a statue.)
Disney's English dub also has a cast so exciting that I'm actually tempted. Tim Curry plays the Cat King! How can that not be awesome? Can you imagine a better role for him? Meanwhile Anne Hathaway plays Haru, while there's also Peter Boyle, Cary Elwes and (for Buffy fans) Kristine Sutherland.
This isn't a big film. It's a featherweight, charming piece that bubbles along on energy and enthusiasm. It has lots of excitement and narrative momentum (which is something I'd never say about Lewis Carroll, for all his interesting qualities). I'm terribly fond of Haru. It's a breeze. Weird translation choice with the English title, though.