One of the hardest creative acts to pull off is turning a popular novel into a film. It's hard enough to take a story that unfolded over 1000 pages, and render it into a tale that can be told in two hours. It's even tougher if the novel has a enthusiastic and loyal readership. There's no way for a movie to capture what they imagined while they were reading the book.

"Corelli's Mandolin" by Louis De Bernieres is that kind of book. (Did you think I was referring to "Lord of The Rings?" Check back with me in four months.) Since its publication in 1995, De Bernieres' opus has sold more than 1.5 million copies in the U.K. alone. It's estimated that one in twenty British households owns a copy, and it has remained on the British best-seller list since its publication. While Americans didn't embrace the novel that enthusiastically, it still did very well here, both commercially and critically.

This kind of success made it almost inevitable that De Bernieres' story would be made into a film. "Captain Corelli's Mandolin" directed by John Madden, who previously directed "Mrs. Brown" and "Shakespeare in Love," opens on August 17. Prior to seeing the film, I expected something different from the book, and that's what I got. But what matters isn't that the film differs from the book. What matters is how it differs and what messages these differences convey.

The film is set on the Greek island of Cephallonia. It's 1941, and Greece is threatened by Mussolini's Italy from the west, and Hitler's Germany from the north. The central character is Pelagia (peh-lah-gee-ah) (Penelope Cruz), the local doctor's daughter. Despite her father's misgiving, she is betrothed to Mandras (Christian Bale), a local fisherman. Shortly after their betrothal, Mandras leaves to fight against the Italians in Albania. During their time apart, Pelagia's ardor wanes, and she begins to share her father's misgiving about the match.

Although the Greek army defeats the Italians, they are no match for the Wehrmacht. Greece is occupied by Germany, which divides the country with its Axis partner. Italy's share includes Cephallonia, which is how Pelagia's, as well the island's, tranquility comes to be shattered by the sight of Italian troops marching through the streets. One soldier in particular, an artillery captain, unnerves Pelagia. Not by an act of brutality, but by having his company turn and face — actually admire — her as they walk by.

The order, "bella bambina [beautiful girl] at nine o'clock," tells us most of what we need to know about the mandolin-playing captain, Antonio Corelli (Nicholas Cage). He may have arrived with an occupying force, but he's no occupier. In fact, he's not much of a soldier, either. Still, he's an Italian, and that means that Pelagia must hate him, which she works at, especially after he is billeted in her home.

As theatrical trailers and television spots have told you by now, Pelagia and Corelli eventually fall in love. But their romance is interrupted by Mussolini's overthrow and Italy's subsequent surrender. As Corelli and the rest of the Italians prepare to hand over the island to the Germans, the question on everyone's mind is: will the Germans let them leave? Corelli, unlike his superiors, has his doubts. His doubts are eventually confirmed in the way you would expect from the Third Reich. Comparing a film to the book it is based on may seem unfair and even besides-the-point. As I said at the top, they're very different art forms. But the choices directors and writers make about what to retain from the book and what to discard can be revealing. Especially when, as is the case here, those choices are completely at variance with the author's perspective, and turn important parts of the story on their head.

Of all the places the book and film part company, the most telling is in their respective ideas about love. They're not just different from one another, they're polar opposites. It's as if the film makers said "De Bernieres may have sold millions of copies, but we know better." Well they don't. And their changes are a reminder of why movies are the last places we should look for guidance on love. In the novel, love is principally defined as the willingness to put the other person's well-being and happiness above your own. Thus, love's primary manifestation is the willingness to sacrifice yourself on their behalf — whether they know you love them or not — and being content to leave it at that, if that's what circumstances dictate. This gives love both a moral and a tragic dimension that you seldom see depicted on the screen.

In the film, love, as it is in nearly every movie, is a feeling, a combination of physical attraction and emotional attachment to the other person. It's clear that people care deeply for one another. What's not-so-clear is what that caring requires, especially if it's not reciprocated.

In De Bernieres' book, the love between Pelagia and Corelli doesn't exist independently of those around them. She's still Greek. He's still an Italian, and their countries are still at war, no matter how they feel for one another. They are mindful of the obligations and consequences that flow from being part of a larger community. In the world De Bernieres created, like in real life, love is situated. It doesn't make the rest of the world go away.

This sense of the context in which romantic love occurs is missing from the film. There's no consideration, or even mention, of any fallout that might come from a relationship between one of the occupied and one of the occupiers. Every one is a kind of emotional free agent, free to love whomever they please, with the exception of Nazis, and any objections to their choices are the products of prejudice. In other words, love is a private act with no social or communal dimension.

Then there's the relationship of sex to love. The novel is full of romance and even sensuality. But it's also chaste. That's not to say that the characters don't feel sexual desire. It's that they aren't ruled by those desires. As De Bernieres put it, "[Corelli] loved her too much to jeopardize her happiness." He didn't want to risk getting her pregnant until they could be married, especially since abortion was out of the question. As Pelagia's father, the doctor, put it "[abortion] is the murder of an innocent."

In contrast, within thirty seconds of the first "I love you," the on-screen Corelli and Pelagia were taking their clothes off. I can't say I'm surprised. Disappointed, yes. Surprised, no. In contemporary popular culture, sex and love have become almost synonymous. Sex is what people do when they love each other. That certainly was the case in Madden's Oscar-winning "Shakespeare in Love."

That love can exist without genital sex is an idea the "creative community" has trouble getting its mind around. As a result, the world depicted in most films isn't only morally impoverished, it's, for lack of a better word, romantically impoverished as well. "Love" becomes one-dimensional. And when it has more than one dimension, it's still shallow. There's very little sense of why, beyond a physical attraction, one person "loves" another person. And there's even less sense of their attachment's enduring or sacrificial qualities.

This wouldn't matter if so many people didn't take their cues on the subject from movies. But they do, and that's why I'm disappointed in "Captain Corelli's Mandolin." Not because it differed from the book, but because it had a chance to transcend the film industry's usual mush and twaddle on an important subject and passed. That's why, if you're looking for lessons on life and love, you shouldn't wait for the movie.