The tremor of forgery is the thirteenth of Patricia Highsmith's 22 novels and about the tenth I have read. It first appeared in 1969. On the cover of this one they quote Graham Greene to the effect that this is her best, which I was doubting for much of the book but I found the final 10 chapters or so both gripping and full of interest as nce more she explores the whole area of morality and conscience. Those final chapters, of course, only work because of the long set up that precedes it.
This passage struck me
Ingham had a sick feeling he hadn't experienced since adolescence, when he had looked into some religious books at home, dusty old things that must have belonged to great-grandparents. "Repent your sins ... bare your soul to Christ" The questions and answers had assumed that everyone had sins, apparently even from birth, but what were they? The worst Ingham had been able to think of was masturbation, but since at the same time he had been browsing in psychology books which said it was normal and natural, what was there left? Ingham didn't consider that what he had done that night had been a sin or a crime, if he had killed the Arab at all, which would always be not quite certain, until someone actually found the corpse.
When we try and speak to people in terms of biblical morality, it is often an uphill task. Only a truly biblical world view gets things in the right perpective.
This is a theme Highsmith almost endlessly explored.