Innumeracy, at a mere 135 pages, jumps in with easy math play. Paulos didn't want a mathematical Cultural Literacy with lists, but an immersion in what being math literate means in attitude and application. Clearly, he sees mental math as fun and the prerequisite to mastering what's necessary; since without some joy, there is little interest in learning enough math to protect one's mind from deception and to gain the tools necessary for interacting with the modern world.
Intermixed with play are quick comments on what should be taught such as Discrete Mathematics (not the conventional push for Calculus), and the very real need for Probability and its Applied Mathematics cousin, Statistics. Paulos, like others such as Mlodinow, realizes the danger in humans seeing patterns where there is only randomness. We need Statistics to detect error within ourselves; not just to detect errors in arguments by others. To put this differently, a mathematical mind isn't about tricks or computation, but how see, how to obtain the heuristics needed for problem solving or merely seeing problems where others have no vision.
Showing how math play leads to value, Paulos proposes models on what having numeracy can exhibit: for example, a logarithmic safety index for rating everyday risk, but he never says "model this." He treats the reader with respect.
Each chapter of the book (1988) presents an area where innumeracy leads to error in different aspects of modern life. This isn't a must read. Those who know, know. Those that don't, probably wouldn't pick it up - sadly.