As simple as possible to summarize the best way you can, first, please. Feel free to expand after, or just say whatever you want lol. Honest question.
AA is a great program and is basically secularized Christianity. Two great religious books that talk about the program from a more explicitly religious perspective are "Breathing Underwater" (Catholic) and "Steps of a Transformation" (Orthodox). Even with your agnostic perspective I think you would find them enlightening.