Your Money or Your Life by Vicki Robin

Your Money or Your Life (1992, revised 2018) is the philosophical foundation of the FIRE movement and the earliest published framework for thinking about money as life energy. The central framework: every purchase decision is a trade of your finite life hours — so the real price of anything is not dollars but the hours of your life you traded to earn those dollars. This reframing produces a radically different relationship with spending than standard budgeting approaches. The book predates index funds as mainstream products, so some investment specifics are outdated, but the conceptual framework is timeless. The chapter on calculating your real hourly wage — after accounting for job-related costs, commuting, decompression time, and status spending — is one of the most clarifying financial exercises available and has been adapted into dozens of subsequent frameworks.