It might seem odd that the other review of this book ('Lucid and brilliant') describes her moral philosophy as "a kind of Anglican conservatism" since Dame Iris was an atheist. However, I have to agree that she could largely stand in the tradition of Bishop Joseph Butler (1692-1752), the great Anglican theologian and philosopher, who largely represents what might be considered traditional English or Anglican moral ethics. The similarities are due to the fact that Murdoch, while an atheist, was not a materialist by any means. She was a Platonist -- in about as pure a sense as you can imagine -- and Platonism was/is highly influential in Anglican (not to mention, Roman Catholic) thought. While she does tweak Plato a bit, her moral realism is amazingly congruent with that of Plato. For instance, she speaks much of the Good as that which we must direct our attention and even love towards. Naturally, she attacks the dominant moral theories of the modern era -- deontological/Kantian and utilitatarian ethics -- in much the same way that G.E.M. Anscombe did in her essay, "Modern Moral Philosophy" (1958), which revived virtue ethics. If you enjoy Miss Anscombe or other similar, pro-metaphysical moral philosophers of the 20th century (such as Simone Weil or Alasdair MacIntyre), then you will surely enjoy this book.
In 1992, Iris Murdoch (who mostly wrote novels) expanded her ideas on ethics in her book, 'Metaphysics As a Guide to Morals.' This is a much larger work and would greatly benefit from reading The Sovereignty of Good first. All of her essential moral concepts are found in The Sovereignty of Good, in a clear and succinct manner. However, her views, like all philosophies, are not without criticisms. The best collection of critical (both positive and negative) essays on her work is 'Iris Murdoch and the Search for Human Goodness,' which was born out of a conference on Iris Murdoch held at the Divinity School of the University of Chicago in 1994. It includes essays by some of today's leading moral philosophers and theologians, including Charles Taylor, Martha Nussbaum, Stanley Hauerwas, and William Schweiker. For a full treatment of Iris Murdoch's moral philosophy, see Maria Antonaccio's 'Picturing the Human: The Moral Thought of Iris Murdoch.' Both of these books are excellent and essential for anyone doing an academic study of Dame Iris.