I've dipped in and out of this book before, most significantly when studying Raphael's, The School of Athens. This is the first time I've read it cover to cover. It was tough at times, sometimes ideas are packed tightly on the page, but immensely rewarding. Given the subject matter this introduction is highly accessible and even encourages a layman to critique the ideas of great thinkers, I wanted a pen and paper half the time I was reading to put down my thoughts on Plato, or arguments about God.
The only problem with this book is the length of the reading list it left me with, including: John Stuart Mill, Mary Wollstonecraft, Hannah Arendt, David Hume, Plato, Heraclitus, Confucius, Adam Smith, Hegel, Comte, Karl Marx, Theodor Adorno, Simone de Beauvoir, John Rawls, Bertrand Russel, Michel Foucault, Noam Chomsky and Lyotard. Oh dear, where to begin.