Will Smith, miscast but still delivering a reasonably solid performance, stars as Robert Neville, a military scientist who may very well be the last human being on Earth. As the film opens, we learn that in the very near future, a scientist discovers what is believed to be a viral cure for cancer. But as I Am Legend quickly jumps ahead three years, to an eerily deserted New York City, where vegetation has overtaken the once booming metropolis, it is clear something has gone terribly wrong. What was once an urban jungle is now pretty much a jungle as Neville, tooling around Manhattan with Sam, his trusty dog, hunts a pack of deer, only to come up empty-handed when he is forced to compete with a family of hungry lions.

From the very beginning, I Am Legend starts out strong, delivering a great variation on Matheson's original concept and narrative. But that's not that hard to do. The earlier versions did it well, as have other films like 1985's under-rated The Quiet Earth and Danny Boyle's 28 Days Later, which are among the many films to borrow heavily from Matheson. (For the record, George Romero was very influenced by I Am Legend when he made his zombie films, especially Night of the Living Dead and Dawn of the Dead, so any films that draw from either of those, are really drawing from Matheson's work). The problem with some of these other films--especially the previous adaptations--is that they soon fall apart after the first reel. But I Am Legend manages to hold it together, as Will Smith pretty much carries the entire first two acts of the movie with just a dog as a co-star. Several flashbacks establish the chaos as Neville tries to get his family out of the city before it is quarantined off; but those scenes with their massive crowds and supporting cast do not take away from the fact that this is essentially a one-man show. And as Neville goes about his day-to-day survival routine, which includes looking for a way to treat the rabies-like disease that has claimed over 90% of the population, Smith turns in a surprisingly complex performance as a man who has lost his mind from both loneliness, as well as the pressure of being one of the lead scientists whose failure has meant the end of civilization.

I Am Legend is an entertaining film that is not totally faithful to Matheson's book, but still manages to capture a decent portion of the novella's original spirit. At over 50 years old, the deceptively simple book poses many challenges in adaptation, not the least of which is making one man's tale of solitude cinematically compelling. Most of the adjustments and changes to the original story are acceptable conceits, the notable exception being how the film treats the infected mutants. In the book, the creatures are a vampire society that has grown to replace human beings, and they gather every night outside Neville's home and taunt him. In the book, the vampires are a metaphor of societal and moral change. But in the film, the creatures exists solely as monsters, with only a hint of socialization and sophistication, and not nearly half the depth of Romero's zombies in Land of the Dead. This deviation from the original plot pretty much negates the whole meaning of the title. And if that's not bad enough, the CGI creatures don't have much weight or character. They look fake, and in ten years time will look as ridiculous and dated as the albino mutants Charlton Heston battles in The Omega Man now look.

While the film is running, I Am Legend maintains a solid pace and effectively creates tension. But things take a bit of a turn in the third act that signals a breakdown in the story, and creates a major plot hole that may go unnoticed while you're caught up in the moment, but within an hour of watching the film will make your realize that parts of the script are very poorly written and conceived--so bad, in fact that it threatens to mess with the rest of the film.

Whether or not I Am Legend will withstand the test of time is still up in the air--although my money says it won't. It may not even hold up to repeated viewing. But it is entertaining and effective enough in its own right that it is worth watching. Just make sure you read the book.