I haven't seen this movie yet, but recently watched a DVD of the original screen adaptation, starring Vincent Price, called The Last Man on Earth.
In the DVD it has an interview with the author, seemingly made just before the making of the latest, Will Smith, version, and he emphasized that there were quite a few delays in producing the first, because it was not the kind of movie Hollywood likes to make (the 1964 version was made in Italy.)
However, from what I have read elsewhere, all of the three versions (which were written by the author) seem to have copped out in regard to the central theme of the novel, which is, who is the "monster" and who is the "victim" is a matter of perspective.
I will try to get time to find and read the book, and compare it with the films to see if this is true.