If you are a fan of Hans Christian Anderson, I think you'll like Helprin's old fashioned retelling.
Personally, I'm pretty mixed about it. I'm generally not a fan of Anderson's overly wrought, pedantic style, which Helprin imitated. I also didn't like the Helprin's strictly rational approach, stripping away all magic but the wonder of Nature; nor did I enjoy Helprin's shift from fairy tale narrative to parodying, satirizing, and hyperbolizing the aristocracy (which is particularly odd since there aren't any royals to lampoon anymore. So who exactly is this parody for?).
What did I like? I liked the themes, and the thematic weight Helprin gave to the characters: Odette became an allegory for simple, homespun, wholesome peasant life; a wild girl, though one far more in keeping with Rousseau's vision than Miyazaki's. The court--I suppose represented by Odile, though she's hardly in it?--representing excess, gluttony, vanity, and political backstabbing. And the prince, caught between the two, who loses his way but finds both redemption and tragedy. Van Allsburg's paintings are quite good, though squandered on such minor parts of the story.
It's really not a bad story, nor is Helprin a bad writer; it just wasn't at all what I expected. I like Helprin's attempt at filling out the backstory, I just think he got too focused on that and lost the narrative thread.