Let the publisher be your guide.
It's by Penguin Press -- it's for someone who's browses a half-price book store and gets the idea that some familiarity with pre-socratic philsophy is something they want to add to their lives.
It lacks the critical richness of other works (I enjoy Patricia Curd et. al's ANCIENT GREEK PHILOSOPHY) -- so if you want depth, you won't find it here.
I read this book as part of an ancient greek philosophy class and I hated virtually everything on the reading list. This book was part of said curs-ed list.
Our present knowledge of the Presocratic philosophers is all second-hand: it consists of attributions made in later classical literature by a wide variety of authors, from pagans, like Aristotle and Iamblichus, to Christians, like Clement and Hippolytus. This book gives the reader who has been tantalized by these fragmentary citations a chance to view these quotes surrounded by the contexts in which they are preserved. That is both the strength and the bane of this volume. For instance, it is interesting to note how often Heraclitus is referred to as "obscure", but then, how much of what is attributed to him was actually said by him, how much does the citation represent the quoter's bias or training, and in what context or order were the sayings originally delivered? We will never know. So, if you have a passing acquaintance with the sayings of Zeno, Pythagoras, Empedocles et al., this may be the book to draw you deeper into the mysteries. The beginner may be merely mystified by the Presocratic palimpsest.