Caroline Criado Perez documents how a world designed around male bodies and experiences systematically disadvantages women across every domain of life. She reveals that data gaps, the absence of sex-disaggregated information, lead to products, policies, and systems that treat men as the default human and women as deviations from the norm. Crash test dummies modeled on male bodies mean car safety systems protect men better than women. Medical research conducted primarily on male subjects leads to drugs that work differently in female bodies. Workplace policies designed around male career patterns disadvantage women who bear children. Perez draws on research from economics, medicine, technology, and urban planning to show how these gaps compound, creating disadvantages in time, money, and health. She examines how smartphones designed for male hands and voice recognition trained on male voices exclude women from seamless technology use. She shows how economic measurements that ignore unpaid care work undervalue women's contributions. Throughout, Perez emphasizes that these are not malicious choices but rather the invisible consequence of treating one sex's experience as universal. The book provides both rigorous documentation of systemic problems and a call for better data collection that would make women's experiences visible and addressable. Perez writes with controlled anger and dark humor, making technical subjects accessible while building an undeniable case for change.