It seems that he covers most of the major positions and philosophers in a general and non-technical way; his choice of philosophers to discuss seems very good. But, once you have a general impression, then it is necessary and beneficial to begin to read the philosophers themselves, to read more thorough expositions and commentaries.
If you are just beginning to find your way in Philosophy, you could do worse to read the originals by Mill then perhaps Descartes and Kierkegaard as these philosophers avoid a lot of jargon and do not presuppose a major background in the history of philosophy to understand their positions.
Above any others, Plato's Apology of Socrates is in so many ways the cornerstone of all philosophical thinking that it must be read. Whitehead remarked that all philosophy is a footnote to Plato, so also read the Republic.