I Am Legend tells the story of a viral outbreak (resulting from a supposed cure for cancer) that effectively wipes out over 90% of the world's population, turning the remaining humans into agile and highly aggressive vampires-like creatures. Of the very few who are found to be immune to the virus, scientist and army general Robert Neville (Will Smith) eventually believes himself to be the last man on earth, roaming the streets of New York with his loyal German Shepard, Sam, by day hunting for food, scavenging for supplies, and laying traps to cover his tracks. When night falls, however, Neville is confined to his barricaded home to search for an antivirus in his basement lab while the screams of the infected rage outside in the streets.

Despite deviating into clichés slightly in the last act and suffering from some poor cgi work, I Am Legend is mostly a very good film. It works on the level of a pure post-apocalyptic action/horror film in that it's gripping, tense, and exciting, but more importantly it succeeds based on its humanity. Smith gives an affecting, isolated performance reminiscent of Tom Hanks' in Cast Away, in that he carries the entire first hour of the film (aside from a couple of brief flashbacks) with no other human characters to interact with. His bravado solo performance here is really the reason to watch.
From what I understand of the novel (which I have not read), it takes a far more ironic and depressing take on the material which would have been nice to see in the movie. The character's crisis of religious faith is more of a forced afterthought in the film than an integral part of the character, and the ending of the book (which gives it its title) changes both in outcome and in meaning. That's not to say the movie is stupid; in fact, there's one scene in particular where we are first introduced to the "vampires" that is particularly telling about the values of society. Smith's character, walking through an abandoned building steps on a pile of money, which drives society but in this context has become completely worthless; he later remarks how the infected humans have lost all remaining aspects of human behaviour. Flashback scenes of the first stages of infection show a chaotic society on the verge of deviating into barbarism, not unlike the scene in Spielberg's The War of the Worlds where the crowd mobs the protagonists van. However, ultimately I Am Legend could have done something better in the end rather than falling victim to a typical Hollywood ending.
As it stands, I Am Legend is well worth seeing, though it lands slightly below another film inspired by the same source material, the exceptional 28 Days Later.

Recommended:
Yes

Video Occasion: Fit for Friday Evening
Suitability For Children: Suitable for Children Age 13 and Older