The way in which securities are traded is very different from the idealized picture of a frictionless and self-equilibrating market offered by the typical finance textbook. In Market Liquidity, Thierry Foucault, Marco Pagano, and Ailsa Röell offer a more accurate take on the liquidity of securities markets, its determinants, and its effects. They start from the assumption that not everyone is present at all times simultaneously on the market, and that even the limited number of participants who are have quite diverse information about the security's fundamentals. As a result, the order flow is a complex mix of information and noise, and a consensus price only emerges gradually over time as the trading process evolves and the participants interpret the actions of other traders. Thus, a security's actual transaction price may deviate from its fundamental value, as it would be assessed by a fully informed set of investors. Market Liquidity takes these deviations seriously, and explains