How the Immune System Works is composed of nine chapters (or 'lectures') written in a direct lecture style. The first lecture is an overview of the immune system designed to give students a glimpse of all the immune system players on the field at once. The next five lectures focus on the individual players of the innate and adaptive systems. In the seventh lecture the author shows how all these players interact with each other. The final two lectures serve as a review, as students use the concepts that they learned in the first seven lectures to examine three interesting topics: cancer and the immune system, transplant immunology; and the immunology of pregnancy.