In my study of Wittgenstein's later philosophy, the one book I have found to be the most helpful was Pitkin's. Perhaps because she works through the implications of Wittgenstein's radical philosophy for a particular set of conundra. She weaves together a tapestry from, it seems, a 1000 sources. Her use of source is amazing. Her quotes from Cavell's book are better than the book itself; that is, the bits and pieces she picks, and the order and context she provides for them, is far more coherent than the book itself. The same could be said for her presentation of Wittgenstein, of whom it could never be said that he explained his ideas clearly. Nevertheless, he got it right, and to this day few apreciate the fullness of his critique of modern philosophy or its implications. Pitkin does.