What is great about this book is that it immeadiately engages you in ancient debates, which is what ancient philosophy is about. Do you really want a list of names and principle doctrines? There are plenty of books like that. There was a different consciousness in ancient times; to read ancient philosophy through our modern consciousness is to misread it. This book helps to engage the reader as the ancients engaged in their philosophy.
This little pamphlet is the first philosophy work that I have ever read, and Prof. Annas wrote it for people like me.
Her intention is to help people engage with the thoughts of the ancient (Greek) philosophers, and to show how the questions with which the ancients grappled are the same questions that we ask today.
I have a somewhat better understanding of Plato, Aristotle and the Stoics. Am I a better person? I do not know. Did the ancient Greeks tell me anything I did not know already? Maybe not.
Yet I think Prof. Annas might say, along with the ancient Greeks, that philosophy is worthwhile even if we derive no benefit from it at all. This is a book about those who practiced philosophy for its own sake.
So I would say that a beginner such as myself ought by all means to engage with both the ancient Greek thinkers and Prof. Annas's exposition of them. You might find yourself wanting to learn more and more about the ancient thinkers, without being sure why.