I've always thought of it as an evolution from henotheism.
However, I have heard of your idea as a cult to follow Akhenaten's rule. Akhenaten was purged from history by the priest class, a curse put upon anyone who said or wrote his name, and so Jewish monotheism was said to have been his legacy. Again though, I agree with the progression from henotheism.
Edit:
Cork, i see why you think you are right, but you are wrong. Moses was alleged to have been a contemporary or inspired by Akhenaten who instituted monotheistic reforms in Egypt. This of course welcomes the idea that the biblical narrative is false and not at all historic.