When it opens Friday, "The League of Extraordinary Gentlemen" will be the fourth film this year based on a comic book, following on the heels of "Daredevil," "X2: X-Men United" and "The Hulk." That has me thinking about why some adaptations succeed while others fail, and I'm not thinking only of adaptations of comic books.

Take a movie like "Adaptation" starring Nicolas Cage. It's a brilliant film in its own right; it earned an Oscar nomination for best adapted screenplay. But it's a lousy adaptation of its source material, Susan Orlean's non-fiction book "The Orchid Thief."And if you've seen the film, you know why: It's not "The Orchid Thief" at all. Rather, it is a movie about the making of a movie of "The Orchid Thief."

Then there is "Daredevil," which is reasonably faithful to the Marvel comic book but is a bad film, even when judged by its own goals, which, admittedly, are far less ambitious than those of "Adaptation."

"Daredevil" commits many cinematic sins, but the worst is that it tries to do too much. The film's core story is based on Frank Miller's "Elektra Saga," yet its first third is preoccupied with the completely unrelated tale of how a young Matt Murdock gains the superhuman abilities that allow him to become Daredevil. So, unsurprisingly, "Daredevil" seems like it should be two separate movies, especially when it reaches its conclusion and tries, unsatisfactorily, to tie back into Daredevil's origin story.

It makes you appreciate how Tim Burton handles Batman's origin in the first of his "Batman" movies. One brief flashback is all it takes.

To compress years of comic book plots into one two-hour movie means making changes.

"X2" is less faithful than "Daredevil" to the letter of its source material but more faithful to the spirit. As it turns out, few "X-Men" fans care that "X2" radically alters no fewer than three "Uncanny X-Men" stories in order to make one cohesive whole —as long as the spirit of each remains.

Still, fans are nothing if not fickle, and they're split on Ang Lee's "The Hulk."

Here it's about whether or not "The Hulk" lives up to the spirit of the comics. Fans who think that the comics are primarily about Bruce Banner's psychological problems, which manifest physically as an angry green giant, love the film. Fans who think the comics are primarily about the Hulk getting into fights with other gamma-irradiated monsters and smashing things hate it.

Hardly anybody quibbles over the literal deviations — about how Betty Ross shouldn't be a scientist or about how Glen Talbot shouldn't be so slimy.

But when a movie fails to live up to either the letter or the spirit of its source material, look out. Disaster lies ahead.

That's the case with the 1998 American-produced version of "Godzilla." None of the details are right. Instead of a 40-story-tall, fire-breathing dinosaur who stomps his way through the Tokyo skyline, we get an asexual iguana who lays eggs, runs from the enemy and burrows beneath New York City.

Such radical changes are already enough to sink the film, but "Godzilla" doesn't even get the overriding theme of the original right. The Japanese "Godzilla" is a parable about the horrors of nuclear war. The American "Godzilla" is a textbook example of soulless Hollywood filmmaking.

If there is a lesson to be learned from all this, it's that you can be both too literal and not literal enough when adapting something into a movie. But you can never be too true to your source material's spirit.

Unless you're making a movie about orchids.