Okay... (*deep breath*)
I read the book some years ago at the prompting of my sweetie. I rather liked it. And if you've read the book, you know that the only way to make a movie out of it would be to have Peter Jackson split it up into at least three movies, each no less that 2-1/2 hours long.
Author Mark Helprin (not to be confused with right-wing hack Mark Halperin) has a way of writing about places and environments on a scale that makes words like, "vast," and, "massive," wholly inadequate. The closest imagery I can reach is in the Fritz Lang silent film Metropolis, whose shots of the city and its Babylon Tower suggest that kind of scale. Helprin writes New York City on that scale. It's the same New York you know -- there's an extended sequence in the constellation-covered ceiling of Grand Central Terminal -- but Helprin writes things so that things seem vastly larger, more ethereal, and much more wonderous than their real-world counterparts. Think of the ballroom dance scene in the movie The Fisher King. That sort of thing would be entirely at home in Helprin's New York.
As a consequence, describing Winter's Tale the book is very difficult because of that ever-present ethereal quality. Several of the characters exist "out of time" -- not exactly immortal, but not bound to exist through all the days from then until now. Perhaps a cleaner way to imagine this conceit would be as semi-cohesive spirits who de-incarnate in the late 1800's and reincarnate in the present day. I suppose doing this lets Helprin write a story whose scale matches the environments and places he's writing. It all contributes to the book's near-omnipresent other-worldly feel.
There are also a number of parallel plots running, with [em]many[/em] more characters, and this is where the movie runs into trouble. The love story between Peter Lake and Beverly Penn is just one of several. And though it has significant impact, it is not [em]the[/em] main story in the book. So to make the movie, they had to rip that single story out, snapping all the interconnecting threads and support structure. They apparently then filled in the mangled bits with Spackle and called it a movie.
Here's the smallest example of how bad a mismatch the movie is with the book. When I saw the previews for it in the theater, I and my sweetie (who [em]adores[/em] the book) looked at Russell Crowe's character, and we both immediately thought to ourselves, "Pearly Soames isn't that tall." Now, what that should tell you is that Helprin conjured up some pretty powerful, lasting imagery in his book, because we both [em]immediately[/em] spotted the mismatch. It seems the filmmakers whiffed on the rest of the book's aspects as well.
I'm guessing someone in Whollyodd optioned the book, then tried to give an elevator pitch for a film version of it, and everything in the film proceeded from that pitch -- except that such a pitch is impossible, because the book defies attempts to describe it. I've just spent the last half-hour and five paragraphs failing to do so. Winter's Tale isn't so much about story and plot points, it's about atmosphere and mood and titanic cities and tiny people against the sprawling tapestry of time trying to find their place in it all.
And a supernatural milk horse.
If you want to get a sense of Helprin's writing without plowing through the whole of Winter's Tale, go find a copy of another of Helprin's books, A City in Winter, which is ostensibly a children's book, but still has that same sense of vast scale.