It was the first 'feature film' Spielberg made- he was 24 when he made Duel- and it was originally made for television in 16 days (it did have high production values for 1971 TV)- its success lead to more scenes being filmed for its later cinematic release around the world.
There are many themes you'll find in Spielberg's later films- most obviously Jaws. I don't think the film is amazing, but I do think it's entertaining enough to watch more than once.