This is the second (1803) edition of Malthus' Essay, which is considerably expanded from the first (1798) edition, to the point of being a completely new book. It is truly excellent - well worth your time, even if you have already read the first edition. There is a better edition available than this one though (Cambridge Texts in the History of Political Thought). For some incomprehensible reason, the editors ommited chapters 3 through 12 of Book 1, and ALL of Book 2 from this edition. To read the entire Essay, getAn Essay on the Principle of Population - Vol. 1 and An Essay on the Principle of Population - Vol. 2 ... or, get An Essay on the Principle of Population - Vol. 1 for books one and two, and this edition Malthus: An Essay on the Principle of Population (Cambridge Texts in the History of Political Thought) for books 3 and 4. There don't seem to be any one volume editions of the second edition.