I started David Aaron's Biblical Ambiguities. On pages 92-95, Dr. Aaron discusses Moshe Greenberg's treatment of the burning bush scene in Exodus 3.
According to Greenberg, the fire of the burning bush represents God before Moses---God's "destructive power" and "dangerous holiness," God's "purity" and "illumination," God's "reality yet insubstantiality," and God's "ability to work at a distance". Greenberg also refers to v 2's statement that an angel was appearing to Moses out of the burning bush, and he says that the lesson of the story is that God makes concession to the frailties of human beings, as God's makes himself accessible to them.
Dr. Aaron doesn't care for Greenberg's theological interpretation of Exodus 3. He states that none of Greenberg's ideas "are derivable from the text itself." He says that Greenberg assumes that "every aspect of Scripture can be used to illuminate every other aspect of Scripture, regardless of the genre, context, or intent of the shared passages." According to Dr. Aaron, Greenberg ignores a salient aspect of the story---that the bush is not consumed. Dr. Aaron notes that the burning bush occurs only once in the Bible---perhaps to highlight that its meaning is ambiguous. Dr. Aaron states that "a great many images that were available to the biblical writer and that functioned as part of his cultural vocabulary are now altogether lost to us." He also dislikes Greenberg's emphasis on the angel of the LORD, for, because v 2 "clashes somewhat with the overall character of the event", it was probably "an editor's interpolation, added by someone who was a bit squeamish about direct appearances of the deity." According to Dr. Aaron, "Such insertions are not unusual." Greenberg, therefore, places a lot of weight on something that probably wasn't a part of the original story.
Was Greenberg's interpretation of Exodus 3 legitimate, or was it eisegesis? I think a key part of the story is that God was doing something miraculous to get Moses' attention---burning a bush while not consuming it. Why God chose that image---I really don't know. Indeed, God is a consuming fire in the Hebrew Bible, but the point of Exodus 3 is that the fire did not consume the bush, so can God being a consuming fire actually illuminate the reason for the burning bush's presence in Exodus 3? Regarding the reason, we can only speculate. Perhaps the fire was scary to Moses, and that reminded Moses that God was holy. God's holiness is a part of the story, for God tells Moses to take of his shoes, for he's standing on holy ground.