Three movies have been made (at least) directly inspired by Richard Matheson's classic novella (longer than a short story, shorter than a novel) "I Am Legend". Nobody really has gotten it "right" in the sense of not adding or subtracting significantly from the original. I'll touch on the story elements first then do a bit on the movies and how they changed things.
First of all, there are no zombies. The word is never used, although it fits one of the survivor types better. That's right, there are two kinds of diseased survivors in the book, which is one thing that NONE of the movies tries to replicate. In the backstory, the world does a quick die-off from a sudden wide-spreading disease that kills those who get sick with it, and who come back to life as basically blood-sucking zombies (brain impaired, shambling, not breathing, etc.) The other ones are those that are sick and crave blood too, but haven't yet actually died although they eventually are doomed to do so. They can talk and are not brain-dead stupid, but all must hide from the sun and go comatose during the day. No numbers are given but it is implied that the latter group is much smaller and dwindling.
One thing that the movies attempt but don't get right is just how psychologically screwed up the main character is. He lost his wife to the disease and had her dig her way out of the grave and try to eat him, and later his daughter too, but who stayed dead because by then all bodies had to be burned. The man drinks almost every day, many times to oblivion. He has wild mood swings ranging from despair to violent rage. His mind becomes so wild that when he later gets some clues about the science behind the plague it's hard for him to think logically and to concentrate for any extended length of time.
So the guy hides in his fortified house by night as the hordes rage around him, but forages during the day for food and other supplies, pretty much like all the movies. Another thing the movies do that the book doesn't is have lots of guns. The undead in the book have tough skin that is sort of glued like rubber, which just absorbs bullets beneath the skin causing almost no damage. So the guy kills them the old fashioned way, wooden stakes to the chest during the daylight hours. It mentions that one particular day when looking for hidden vampires he kills 47 of them. He doesn't do this every day, but often enough, and the story takes place over maybe 10 years, so he's killed a lot of them.
One day he sees a dog in the daytime (so it can't be undead), but it is scared of him. He spends weeks luring it with food, trying to get it to let him treat it's wounds and malnutrition. He eventually does earn the dog's trust. It dies a week later. This does not help his state of mind, of course.
One day he sees a young woman walking around in broad daylight. Amazed to find another survivor he chases her down and has to physically capture and restrain her because she is so scared and distrustful. Like the dog. He takes her back home and gains her trust a bit and they talk, but things sound suspicious to him. They get along for a couple days, and she seems like a normal person, but he wants to do a blood test on her which she refuses, but he eventually forces her to take.When he's about to read the results in the microscope she smacks him unconscious and runs away. She left a note of explanation.
In her note, she says that she is one of the not-dead-yet vampires, and that they are developing tools to stay in the sunlight (she used dark liquid tan lotion) and medicine to lengthen their lives and someday maybe cure the death side-effect of the disease, although they will still always be blood-drinking vampires. Also, that their numbers had dwindled down due to death and violence (and he is a major cause of it, not distinguishing between the two types since he believes they all will die eventually anyway. Her husband was one of his many kills.) until recent advances. Now they are growing and will someday exterminate all their real-dead cousins and re-create society, and she begs him to leave before they come for him too sometime soon.
He's not able to do that, of course, being too stuck in his ways. And when the genocidal violence comes later, he is captured. As he is brought forward for execution before the crowd of men, women, and children he sees that they are all terrified of him. And as he's about to die, he realizes that he has at least left one lasting legacy for mankind. He says to himself "I am legend." The End.
OK, now for the movies:
"The Last Man On Earth" (1964) starring Vincent Price.
I've not seen this one, but based on the extended review by R3 (does he ever NOT do extensive reviews?), it sounds like it is maybe the worst movie overall, but the one that closest follows the details, using some dialogue and flashbacks from the book. They ending is closer, but the last line about the title is different, maybe because the movie title is different. Whatever.
"The Omega Man" (1971) starring Charlton Heston.
One of my favorite movies as a kid. This one is only loosely based on the book, and gets almost all of the original details wrong, including extended use of guns, the crucifixion ending and hope for original mankind to live. Despite starring the eventual NRA president, this movie is a hippie love fest.
"I Am Legend" (2007) starring Wil Smith.
This one is closer than Omega Man, and gets some of the details from the book right, but again, blazing guns, only one type of monster, and more importantly, the main character is the hero in the end and not revealed as the real bad guy from the new perspective of future society.
This is a pretty long review for me, and I don't go into all the religious symbolism, psychological meaning, and political leanings that a review by Rebuplibot 3 would have. I just don't see all that when watching movies or reading. At least not to the level he does.
Will conservatives like this book?
Well, it was written in 1954 and although it had some wildly new ideas for the time, the main character is still pretty much a golden age conservative father figure. He loves his family, he likes dogs, he owns guns, and doesn't even attempt to have sex with the woman he eventually finds.