Sam died

that Neville was partly responsible for the virus? I know it was never really addressed, but it would explain his suicide move at the end.

Robert Neville lives in California, in a suburb of LA (Compton, maybe... I can't recall, but the book was written before Compton evoked the images it does now). A plague, likely caused by bacteria, has apparently wiped out almost all the people on the planet, and the people who weren't wiped out were turned into ravenous creatures who can roam only at night (vampires, for all intents and purposes). Neville's wife and child both succumbed to the bacteria and died.

By day, he scavenges for food. He also hunts down the vampires and destroys them, usually by traditional methods (stake through the heart, dragging them into sunlight etc.). By night, he remains inside of his fortified house. He's constantly tormented by the vampires outside; the vampires in this version are at least somewhat intelligent, and they constantly try to entice him to come out. In particular, his old neighbor and the female vampires are the worst; the females constantly try to entice Neville outside by offering him sexual favors, which is especially torturous for Neville due to his isolation. The constant solitude, combined with his nighttime torment, leads him to alcoholism and thoughts of suicide.

Neville eventually sets out to discover what caused the plague. He essentially teaches himself science, pilfering lab equipment from around town to do research. He determines that most of the physical changes are caused by the bacteria. But he also discovers that some of the changes are psychological (the vampires' aversion to garlic, his observation of one trying unsuccessfully to "turn into a bat and fly" by jumping off a lamp pole and flapping his arms), because the victims of the plague believe themselves to be vampires. That psychological dementia probably saved Neville's life, as if the vampires had been cogent, they would have probably just burned his house down.

At one point, a dog who has managed to survive appears. While at first, it is scared of Neville, over a period of days he eventually begins to coax it closer and closer. He eventually captures it, but it's infected, and it dies a week later.

Shortly afterward, Neville sees a human wandering the streets during the day. She, like the dog, runs. He chases her down and basically attacks her, bringing her back to his house. Once there, he has a difficult time readjusting to being with another human; he's also distrustful of her. I may be hazy on what happens, but I seem to recall her knocking him out and leaving his house. When she leaves, she deposits a note for Neville to find.

The note basically tells him that she's an infected as well, but some of them have retained their mental faculties and managed to devise a way to go out for limited amounts of time during the day. Otherwise, they also have to sleep during the day, and while doing so, they are indistinguishable from the normal vampires. She tells him the other similarly infected will be coming for him, and she warns him that he should flee.

He chooses not to flee, and they do eventually come for him. In the process, they slaughter the vampires who have been loitering outside of Neville's house. During this assault, Neville feels a strange sense of attachment to the monsters outside and laments their death. The intelligent vampires also wound Neville in the process by shooting him. They take Neville away to await execution. While awaiting execution, the female brings him drugs so he won't feel any pain when his time comes.

During this time, Neville comes to a realization. He observes that the intelligent infected are slowly rebuilding society. He also realizes that, since he couldn't tell them apart from the regular infected, he's likely killed a great many of them over the years. Just as the vampires that supposedly haunted earlier human society were legend, he realizes that, as he stalked this fledgling society while it slept, he had become legend as well.

Neville isn't in any way related to the cure for the disease, neither before the pandemic nor after. He wasn't even a scientist, much less the military scientist who was responsible for the cure. He was an ordinary citizen caught up in the disaster.

His family died to the disease, not some helicopter crash.

He was in a suburban environment. The vampires knew where he lived and tormented him.

The vampires were not uber-Gollums. They weren't hairless, super strong, acrobats. They were vicious, but they were like humans in appearance and physicality. They retained their ability to speak, but they also suffered from dementia that kept them from formulating complex plans. They were resistant to certain things, like bullets, but nearly all of the traditional vampire defenses worked on them, either because the physical change to vampire introduced new vulnerabilities, or because the vampires actually believed themselves to be vampires (and were thus afraid of things they knew vampires should be afraid of, like garlic).

He was far from the thriving (physically) survivor of the movie. He certainly wasn't spending his mornings exercising or doing recreation. He was drinking himself into oblivion most nights, and he was going through the motions during the day to survive.

There was a dog, but it appeared briefly to give Neville hope, and then it died. It wasn't a companion in any way, much less a remnant of his pre-plague life and family.

There were 0 other humans in the movie. The one who showed up, as I said, was a spy sent by the intelligent vampires. I kept expecting the one in this movie to reveal that, but she didn't.

There was no "safe zone" or refuge. The book ends with the start of the vampire society, not the resurgence of the human society.

The title meant something completely, completely different.