To the average investor, playing the market seems like a high-stakes, high-risk gamble, with success tied almost wholly to luck. In Rational Investing, the asset manager Hugues Langlois and the finance professor Jacques Lussier prove otherwise, showing how anyone can study, predict, and learn to master investing. While luck is no small component of profitable asset management, skilled investors can minimize its influence over time, reducing good and bad luck to minor computational noise. Langlois and Lussier construct a science of smart investing around four considerations: skill, behavior (investor and market psychology), horizon (short- or long-term investing), and luck. Successful practice means learning how to efficiently balance risk premiums, statistically diversify, and take advantage of mispricing'luck is only a small factor. With clear examples from model multi-asset-class portfolios, Langlois and Lussier show how to implement performance drivers from the perspective of an institutional investor with access to extensive resources, as well as a nonprofessional investor who is constrained to single stock and other small-scale purchases. There are few investment products or management strategies, whether traditional or alternative, discretionary or systematic, fundamental or quantitative, that cannot be analyzed through their framework. Langlois and Lussier illuminate the structure of financial markets and the mechanics of sustainable investing so any investor can become a rational player.