David-Hillel Ruben's new book pursues some novel and unusual standpoints in the philosophy of action. He rejects, for example, the most widely held view about how to count actions, and argues for what he calls a 'prolific theory' of act individuation. He also describes and argues against thetwo leading theories of the nature of action, the causal theory and the agent causal theory. The causal theory cannot account for skilled activity, nor for mental action. The agent causalist theory unnecessarily reifies causings. He identifies an assumption that they share, and that most actiontheorists have assumed to be unproblematic and uncontroversial, that an action is, or entails the existence of, an event. Several different meanings to that claim are disentangled and in the most interesting sense of that claim, Ruben denies that it is true. His own alternative is simple andunpretentious: nothing informative can be said about the nature of action that explicates action in any other terms.Ruben sketches a theory of causal explanation of action that eschews the requirement for laws or generalisations, and this effectively quashes one argument for the oft-repeated view that no explanations of action can be causal, on the grounds that there are no convincing cases of laws of humanaction. He addresses a number of questions about the knowledge an agent has of his own actions, looking particularly at examples of pathological cases of action in which, for one reason or another, the agent does not know what he is doing.Inspiring and enlightening in its challenge to received wisdom, and in its convincing defence of some unfashionable positions, Action and its Explanation will be required reading for anyone working in this field.