Nick Maggiulli, chief operating officer at Ritholtz Wealth Management and author of the widely read "Of Dollars and Data" blog, brings rigorous quantitative analysis to bear on the fundamental questions of personal finance: how much to save, when to invest, how to think about debt, and how to build wealth across a career. The book's central argument is captured in its title: the data consistently shows that the best time to invest is now, and that investors who try to time the market by waiting for lower prices almost always end up worse off than those who simply keep buying on a consistent schedule. Maggiulli supports this conclusion with detailed analysis of historical market data across dozens of market scenarios, demonstrating that even an investor with perfect bad luck — always buying at the peak before every major decline — would still build substantial wealth over a full career through consistent investing. The book also addresses the savings-vs-investing trade-off in early versus later career stages with unusual precision, arguing that saving rate matters far more than investment returns for people early in their careers, while the reverse becomes true as assets accumulate. Chapters on homeownership, student debt, divorce, inequality, and the psychology of spending give the book unusual breadth. Data-driven, intellectually honest, and practically actionable, this is one of the best personal finance books written in the quantitative era.