This tells me something about God that was implied pretty much from the moment He planted a forbidden tree in the Garden of Eden: God creates and rules this world without eliminating the possibility of evil, suffering, and sadness. We can ask why, and in this case we have at least some small answer. Satan doubted that Job's allegiance to God was genuine. It isn't spelled out for us, but it seems reasonable to assume that God wanted to validate Job's faith and love by showing that it was real; that Job loved God not because he was rich, and not because he had a great family, but because God was God. But like I said, this is a small answer, because I doubt it would have been any great consolation to Job.
Next, Job's life fell apart, and the way it happened tells us something about Satan, because all the terrible things that happened could easily have been explained by natural or normal causes. One group of people stole his livestock and killed his servants. Then a natural disaster (presumably lightning) destroyed more livestock and servants. Yet another group of outsiders stole even more livestock and killed even more servants. And then a whirlwind killed all his children.
It's not exactly encouraging to know Satan can have control over the actions of armies and the power of weather. And it's possibly even more distressing to think that God would grant him that power. (Is the entire history of the world just a drawn out argument between God and Satan . . . with really compelling theoretical examples?) But it happened. Job lost almost everything.
And the way Job reacted tells us something about him. Job grieved and worshiped. I understand why he would tear his clothes, why he would shave his head. But the worship?
I guess there's something more to God than just the fringe benefits.