"The heart of Saul's sin is [that]... he wants a domesticated god, a god like the genie in Aladdin's lamp, one pledged to do wonderful things for him as long as he holds the lamp. He somehow feels that David now holds the lamp and wishes he could get the power back, but does not perceive that the real God is to be worshiped, reverenced, obeyed, feared, and loved - unconditionally. Here is a man who thinks of himself as at the center of the universe; whatever gods exist must serve him. If the covenant God of Israel does not help him as he wishes, then Saul is prepared to find other gods. This is the black heart of idolatry."
Don Carson on 1 Samuel 28. For the Love of God, vol. 1, meditation for september 4.