Nick Maggiulli's book is the most data-driven on this list. He tests conventional personal-finance advice — lump-sum vs. dollar-cost averaging, whether to pay off debt before investing, how much to spend in retirement — against historical evidence. Several standard answers turn out to be wrong or context-dependent, and Maggiulli is honest about the uncertainty.
Chosen by shared topics, the entries that hold them, and the people who recommended both.

