This is a finely crafted history of ethical and moral philosophy that nicely describes the great philosophers but (unusually in my experience as a regular reader, desperate for an understanding of philosophy but lacking the intellect to hold one together, of any number of histories and overviews and summaries of philosophy) with a welcome eye to the philosophies of civilizations other than the Western.
In the end, he concludes there is no escape from the Euthyphro Dilemma, as formulated by Socrates and recorded by Plato. The dilemma is that good is either good because it is determined as such by some external judge, like a god or a society, in which case it is arbitrary; or it is intrinsically good, in which case it stands on its own objective merits, which we cannot define.
Malik himself thinks that morality is constructed by humans and that our belief in our capacities to carry out that task has been severely undermined by the horrors of the twentieth century and a decline in engagement in collective thinking and discourse. In my own country, the UK, this can be observed in the collapse of trust in polticial processes.
But the journey through this book is more important than the conclusion. It is a serious book, with a nice leavening of humour; and well worth the effort.