Hurrah!!I've been looking for this book for years! It's written for anyone - not just philosophy students - in a clear, direct and personal style. Mr Wartenberg doesn't assume you know about Cartesian or any other principles, so you don't have to read 100 other books to understand what he's saying if you don't want to (but gives you direction if you do). He uses some literary references like Hamlet, but explains the relevence in the text, so no need to read the play (again). There are little potted biographies of key people, as and when they pop up.
Altogether, a really clear and accessible introduction to a complex subject. Excellent.