Apparently Howl is only shown in 8 movie theatres in the Netherlands, which I find odd. I think Spirited Away had a much wider rotation, but that movie is (despite having received an Oscar) emminently Japanese. I mean, kami in a bathhouse, how much more Japanese can you get?
But this movie is not based on an original story by Miyazaki, but on a children's book by Dianne Wynne Jones, an American writer. This means that the method of storytelling is much more accessible to western audiences -- I would have expected Howl to get a wider distribution than Spirited Away because of that.
But then again, what do I know about movie distribution? Let's just say that we were lucky that the local arthouse shows this movie.
The story is about Sophie, who works as a hatter. In the country where she is living, a war is brewing and the city is swarming with soldiers. On her way to visit her younger sister, she is confronted by a pair of soldiers -- but she is 'rescued' by a pretty boy who takes her flying through the air.
Later that night, Sophie is bewitched by an evil witch -- she is made old but can't tell anyone about the magic performed on her. Sophie leaves the city and sets out towards the wilds, where sorcerers and witches live, to seek someone who can lift her curse. Of course, she ends up in Howl's Moving Castle, and meets the inhabitants of the magical castle.
It showed that this wasn't an original Miyazaki story. There were things that were hinted at, but never fully explained (like Sophie's relationship with her mother), and some things are resolved in a rather abrupt manner (the scarerow, the whole war). As a result, the storytelling isn't as tight as we have to come expect from his other movies.
But there are typical things that you just know that Miyazaki is going to do a very charming scene with, like when Sophie discovers how to work the magical doors that allow her to exit the house in four different locations. And the proliferation of ornithopters is another Miyazaki staple.
All in all, the movie is pretty accessible to a western audience. And the expressiveness of the characters, the detail of the backgrounds, all those little things tell us that this is another Ghibli masterpiece. I heartily recommend the movie, though I suspect that one's enjoyment will increase if one is familiar with the book upon which the movie is based.