David Hume is famed for the elegance of his writing style, which stands in contrast to that of some other eminent philosophers. I tried to read Spinoza once and found it completely impenetrable. I am quite sure the fault was mine but accessible is not the word for a Spinoza or a Wittgenstein.
Hume, on the other hand, writes beautifully. This short work, which pretty much delivers what is promised in the title, he regarded as his best work.
He makes a convincing case for putting aside what he regards as the empty theorizing of many moral philosophers, when they try to determine the nature of the good and decide whether morality is natural or man-made. He observes, empirical as always, that all people recognise what is right and what is wrong, subject to a few exceptions, and that morality is grounded in utility – the utility of society. All people live in society and life in a society is simply better if people keep promises and censure rudeness and bad behaviour. It is a deceptively simple argument, elegantly advanced.