This movie is a classic for a reason. Watching the 1974 version now is a funny experience because in many ways it subverts the modern slasher fan's expectations but of course it was made before those tropes were cemented.
The characters have real depth and agency, rare for any slasher film. You truly begin to care about them all which adds to the terror. This film is creepy and gets under your skin in a subtle way, every time the phone rings you are filled with dread as you know what that means.
The way this was framed and shot is masterful, the house looks almost like a gothic castle, the Christmas tree looks as though it is covered in webs, it's almost as if terror could appear at any moment.
There are some excellent performances all round, how great is Saxton as the detective?! I loved this film and would recommend it to anyone.