It's hard to catch a falling star, but it helps if you have a magical binding chain and if the star could walk behind you on her own two legs wherever you wanted her to go. In "Stardust", everyone has a reason for desiring a piece of the star, Yvaine, who though minding her own business, gets accidentally knocked out of the sky in a contest for succession of the throne of the magical kingdom of Stormhold. And that's a simplified version of the movie plot.
To avoid overcomplication, the movie version of Stardust wisely keeps the focus on a single theme: no one is who they appear to be. Some, like the seven princes, have yet to achieve their potential and will kill and be killed trying. Others have their true identities taken away from them by enslavement or enchantment. Captain Shakespeare keeps his secret identity behind a mask of "reputation". Tristan's adventures are partially a discovery of his true heritage and partly a quest for his heart's desire.
Everyone experiences a transformational change, and though they don't necessarily welcome change, they simply accept it and cope with it as a matter of fact. The only ones that don't accept change are Lamia and her sisters (and probably Sisterhood as well). They are driven by their mania to freeze themselves in time, at the point when they were at their most beautiful, by hunting and consuming the warm, glowing heart of a fallen star. In their 400 years of existence, they have no other passion than lying to themselves that time can be cheated; and that's probably why they've ended up such bitter, malicious old biddies -- they never get what they desire.
And Yvaine herself, fallen star, is the only one who has no problems with her self-identity. She knows who she is and isn't shy to make full use of her self-knowledge. She becomes the movie's hottest quest item because of her extremely rare magical qualities, but her real value is in her power to be herself, true to herself at all times. Though that might sound boring, she's also sarcastic, short-tempered and entirely human, which rounds her out, and makes her quite a lovable character.
The plot may be complex, but Gaiman is quite a coherent storyteller. With gorgeous landscapes as a backdrop, and the occasional visual effects surprises (I was quite taken by the drowning-in-air sequence), Stardust is a thrill to watch. It's star shines especially bright as one of the few movies in 2007 that is not a sequel, and is not written to spin-off one either. It's a movie that practices what it preaches -- write it, shoot it, can it, and move on.