Been a while, but from what I recall, the plot is a young man gets kicked out and then encounters the fearsome castle. Which is, of course, actually quite friendly and peopled by strange but fun things.
Heh, shows you how confused I was. It's a young girl who gets cursed and picked up by the castle - the young man is Howl's apprentice. Howl himself is somewhat mopey and likes hats. There's a FireDemon? who becomes a major PlotPoint?.
He gets sent off to... find a meteor, I think. Along the way he falls in love, saves some more odd people and everyone decides to be happy and strange.
There's a sequel. And now, apparently, a cartoon.
About the film, quoted from Ansible 210, whatever that may be - I found this posted on UkMediaAnimationAnime? (a NewsGroup):
DianaWynneJones is ecstatic after a secret premiere of "Howl's Moving Castle", practically on her doorstep in Bristol: `Miyazaki came in person, carrying with him a tape of the film, an interpreter and sundry other shadowy figures (all this was supposed to be secret for fear of the Japanese media, who then descended on me afterwards, so I couldn't mention it beforehand) and we had a private showing at the Watershed cinema. The film is goluptuously splendid with breathtaking animation.
I had grown used to young ladies regularly writing to me to say that they wanted to marry Howl. Now, Howl in the film is so plain stunning and sexy that I think I have joined them. And after the showing and the scamper through Bristol I had a long talk with Mr Miyazaki and it began to seem that we were soulmates.' Some writers have all the luck.
Ansible ? It's an old SF newsletter - must have been going for 25 years or so. Editted by the infamous Dave Langford, it's named after an FTL communications device mentioned in an Ursula K. Le Guin story. The fact that it's also an anagram of lesbian is purely coincidental - Jay
I thought that ansibles were from some of Elizabeth Moon’s books. --Steve
Having seen (and thoroughly enjoyed; probably a tie with SpiritedAway for my favourite Ghibli production) the animated feature: when questioned by the audience, DianaWynneJones was always very careful to say that it was her opinion that plot and character decisions within the film were Miyazaki's prerogative. This is telling. Expect a great StudioGhibli film inspired by the book and capturing its spirit. Look forward to a new plot, infused with Miyazaki's worldview. - MoonShadow
The music is haunting. (Awaiting the films arrival here with baited breath) --Vitenka
Ok. Let's see. Howl is indeed very cute. The whole film looks fantastic. Steampunk and victoriana and sparkly magic and... Don't know where the promotional pictures of 'white bird howl' came from, but human howl and dark bird howl are both fabulous. The plot is, um, kinda loosely based on the book. Not that anyone sane would complain. The last five minutes are a little weak I think (It tied down half a film in 'oh shit, we're late' time). And I have to ask - does anime have to force a war into everything? --Vitenka (Witch of the waste is fabulous! Random puppy is fabulous! Marco is... didn't Marco have his own plot initially? Howl certainly alludes to him also being cursed with his 'everyone here is' line.)
Best line of the film: "He's summoning the spirits of darkness! I saw him do this once before. When a girl dumped him." Best sequence: The whole 'climbing the stairs' race.