The piece I posted is from the first Lubavitcher Rebbe, R. Schneur Zalman Schneerson. In it you can see the differences between older Jewish Mysticism and the later strains. The earlier mystics spend a lot of effort describing the different chambers of heaven and the different angels. R. Schneerson interprets the whole passage metaphorically. He says that concentrating on Angels is like worrying about the refuse, rather than the food. Very interesting contrast with the work of Hekhalot Rabati