Know your superman from your sadist

According to the series editor, Simon Critchley, How to Read books (of which there are at least another eight volumes forthcoming) offer "a refreshing set of first-hand encounters" with their subjects, in contrast with the potted biographies or condensed summaries of their major works (or mixtures of both) that most beginners' guides offer. This claim is partly true, and partly false.

There are many existing first-rate series of introductory books in this field. Phoenix's excellent series The Great Philosophers, edited by Ray Monk and Frederic Raphael, immediately comes to mind, as does Oxford University Press's more recent series of Very Short Introductions, to which Critchley is himself a contributor. Both allow the reader to engage directly with various influential figures. Not all of the first six books in this new series succeed in this aim, though most do.

The general approach is to break each book into roughly ten chapters, each of which begins with a lengthy passage from the figure (I refuse to use the term "thinkers", let alone "great thinkers", for all of them) the book is about, followed by an exegesis that relates it to his or her ideas and other views. (So far the subjects have all been men, but How to Read de Beauvoir is forthcoming.) The success of each volume therefore depends on the appropriateness of the passages selected and the quality of the commentary.

Mark Ridley does a fine job of introducing Darwin in a style as clear and lively as the magnificent prose of the great scientist himself. The focus of the first half of How to Read Darwin is on On The Origin of Species , Ridley guiding the reader through Darwin's arguments for both "descent with modification" (evolution) and natural selection, as well as his responses to what he considered to be the main objections to the theory. Most of the remaining passages come from The Descent of Man , in which Darwin sought to explain social, moral and psychological faculties by appealing to evolution and "sex-selection" (Darwin's one-sided explanation of so-called sex differences), with the final word being given to The Expression of the Emotions , in which Darwin extends his evolutionary explanation to the realm of emotion.

Throughout the book, Ridley expertly handles the double task of reconstructing the intellectual milieu in which Darwin's theory arose and explaining which aspects of Darwin's views are readily accepted by modern scientists and which are contested (or indeed rejected). My only reservation is that Ridley is not critical enough of Darwin's explanations of "sex differences", which completely ignore the role of external factors such as education and socio-political environments in general.

In How to Read Freud , Josh Cohen introduces many key Freudian themes including dreams, jokes, hysteria and the unconscious. The extracts come from Freud's books rather than his (often introductory) lectures and, consequently, Cohen spends most of the time elaborating on what Freud meant, using a number of elusive metaphors himself. The book is informative, but there is little evaluation (let alone criticism) and we are left feeling that Cohen has not really engaged with Freud. Perhaps he intended to leave this to the reader.

Neil Gregor's How to Read Hitler - not an easy book to write - reads effortlessly. Gregor presents us with ten extracts from both Mein Kampf and the lesser-known Second Book , which reveal Hitler's prose to be as hopeless as his logic. We are shown why both books carry an implicit genocidal message but are wisely warned not to let hindsight blind us into reading too much into the texts. Gregor writes with both care and authority; my only criticism is that while he explains why Hitler "can still be read in many different ways for many different purposes", he does not tell us much about who the intended readers of Hitler's books originally were.

I cannot see how Keith Ansell Pearson's interesting book on Nietzsche differs from many other introductions to the moustached philosopher, except that it is more confusing in both its structure and its content. Although each chapter begins with a text extract, How to Read Nietzsche is populated with minor insights in search of a home. In so far as there is any structure, it is a thematic one, though we are told it is periodic. To be fair, the author is writing about a philosopher with over a dozen major publications on more or less the same subject, but this should at least have allowed for an examination of the change and growth of Nietzsche's ideas over time.

John Phillips, who faces a similar challenge with the Marquis de Sade, does better. Nonetheless, we are left wondering why we should read the bad marquis. Phillips does his best to convince us that Sade was a first-rate philosopher and an important and complicated figure, but his views (to the extent that we can safely extract any from his writings) tend to boil down to a crude belief in materialism and determinism, a sick aesthetic and a morality that is chauvinistic, self-contradictory, hypocritical or (and my money is on this) non-existent. Phillips's book certainly gives us a good idea of what to expect, but it is much too charitable to Sade.

Finally, Ray Monk has produced yet another thoroughly enjoyable and informative little commentary on Wittgenstein, with an inspired selection of extracts from various stages of his thought - including his one and only book review, written when Wittgenstein was an undergraduate in Cambridge - each of which is followed by an insightful commentary. The only exception to this rule is the chapter on "What is philosophy?" which is so short it made me think there had been some kind of printing error.

This is a worthwhile introductory series, made more so by a useful chronology and suggestions for further reading. With the exception of Sade (born in 1740), the subjects of these first six volumes all lived and wrote within half a century of each other. Indeed, Freud was heavily influenced by Nietzsche, who was in turn inspired by Darwin's On The Origin of Species . Wittgenstein's Tractatus Logico-Philosophicus appeared in 1921, only 25 years after the last of Nietzsche's books published in his lifetime, and two years before Freud's The Ego and the Id . And Hitler (who was, in his own sick way, also influenced by Darwin) and Wittgenstein were contemporaries at the same school. To understand the full extent of their influence on each other, I therefore recommend that the volumes be read in the following order: Sade (1740-1814), Darwin (1809-82), Nietzsche (1844-1900), Freud (1856-1939), Hitler (1889-1945) and Wittgenstein (1889-1951).

Constantine Sandis is associate lecturer in philosophy, Open University.