Why are we more likely to forgo the opportunity to sell a ??100 bottle of wine rather than actually taking money out our wallet to pay for it, when ultimately the 'opportunity cost' of doing so is the same? Why would the 'endowment effect' mean that we value a free ticket worth hundreds of pounds more than the money we would get from selling it? In this new, ambitious work, Thaler presents his findings in behavioural economics and breaks down the biases and irrational tendancies in our thinking, showing us how to avoid making costly mistakes in life.