Based on the book I Am Legend by Richard Matheson, who also wrote Hell House and that episode of Twilight Zone with the thing on the airplane wing, it's a fast zombie outbreak movie - decades before 28 Days Later so quit saying 28 Days Later invented it. Vincent Price is basically the last man on Earth here, if you define "man" as someone not trying to kill Vincent Price.
I really dig empty places - ghost towns, ruins, disaster areas, derelict buildings, anyplace humans were but are not. Naturally I gravitate toward this kind of movie. And for the first half or so it's a rather satisfying and melancholy sojourn through wasteland Los Angeles as we follow the daily routine of the last man on Earth. He collects food and fuel, burns the fresh dead, tries the radio again, just as he did yesterday and will do again tomorrow. I've lived alone a very long time and find a certain soothing sympathy in this.
The only problem here is the atmosphere is continually challenged by the loud, doodling woodwind section that practically bores a hole in the movie. I guess it's trying to beat you over the head with how desolate the city is and a bit of eerie quiet would violate the principle that the audience will explode if every second of a film isn't scored.
For a movie about the last man on Earth there are a concerning number of actors named in the opening credits, and once the actual plot portion of the movie begins it starts to lose me in the crowd. The flashback to how the outbreak began takes us back to the regular world of family picnics and such, and Vincent becomes a rather generic character lumbered with expositional dialogue instead of the sad, bitter musings that he's the undisputed master of. I'd prefer 90 minutes of him just wandering around the dead city thinking black thoughts.
And yes this is I believe the first outbreak movie, although these would not have been called zombies at the time - I've even heard them called vampires. Even the baser ones are semi-sentient and able to speak a bit. Mostly they say "Morgan! Come out!", but he usually doesn't, preferring to stay inside and listen to records. Not to give too much away here, but there's a whole business about the disease and post apocalyptic society and xenophobia that got a little too involved for me and ultimately devolves into a big loud chase scene to end the movie on a downer, although we do get to hear Vincent defiantly exclaim "You're all freaks! I'm a man! The last man!".