One thing that makes it particularly compelling is that it is the same story told twice, first by the narrator, then by the blighted 'hero' himself. What to the onlooker seems utterly incomprehensible takes on at least a semblance of intelligibility when viewed from the inside. We still can't see things the way he did; but at least we can catch a glimpse of why he saw them that way.
Robert, the son of a fanatical clergyman, believes that the elect of God are immune to sin: 'How delightful to think that a justified person can do no wrong . . .' Armed with this appalling doctrine, he embarks on a mission to destroy those he sees as the enemies of God. Spitefulness, vindictiveness, lies, even murder, are no obstacle to his poisonous crusade.
And through it all his chief mentor is not his father but a mysterious alter ego, 'Gil-Martin'. This is where the story becomes puzzling, for Gil-Martin seems not simply a figment of Robert's crazed imagination, but someone who is real for others in the story. Does Hogg mean us to understand that some kind of demon was literally walking the earth with Robert? Perhaps it doesn't matter - the point is that Robert is first seduced, then captivated, then totally dominated, only to be finally destroyed, by this satanic doppelganger. The moment when he realises at last that he must flee, only to find that he can no longer do so, is one of the most chilling things I have read. It made me understand suicide as never before.
All sorts of questions arise. Where did the author - better known, apparently, as 'the Shepherd of Ettrick', the very epitome of bucolic innocence - get such ideas? Helpfully, he makes a brief appearance in his own novel, representing a no-nonsense, down-to- earth attitude, which is perhaps about the only reassuring thing we find. But still: why read such stuff? Why give such ideas house- room? Such notions may have been current in the 18th century; but today? And then we think of a Jim Jones or a David Koresh, even an ayatollah hurling his fatwas across the globe. Perhaps not so much has changed after all.
If, like me, you read the novel as a Christian, you can only feel that this is the sort of thing that gives all religion a bad name. Andre Gide, apparently, thought it 'astounding', and no doubt found comfort in it for his own unbelief. Certainly it stands as a warning, especially in days when the world seems full of pathological religion. The fact is that thirsty people will drink perforce from polluted wells.