This, along with The Crazies (1973), are George Romero's two more or less forgotten or ignored films of the 1970's. Both are compelling, though the former hews more closely with the themes found in Night of the Living Dead (1968); Martin is much more psychological, and on several levels.
George Romero does Stephen King and directs Stephen King in the Jordy Verrill section of the film (I love Killer Plants!), plus the frame story has Tom Atkins one of my all time favorites!! And...it's a bonafide Halloween film.