During my weeks there I had only two bad nights. Once when I dreamed that the tower was crumpling and, once, sliding forward into machine-gun fire and no pit to creep into, slithering on through mud to mutilating death. And then my screams too joined with the night creatures. Well, there was a third sleepless night but that came much later and for a different reason.I saw the film with Kenneth Branagh and Colin Firth when it came out in 1987, and greatly enjoyed it; the original book is very short, but very intense. It's the story of two shell-shocked veterans in an isolated English village in the early 1920s, one restoring a medieval wall painting of the Last Judgement, the other on a single-handed archæological dig, both confronting and to an extent exorcising their demons. The place and time are very convincingly invoked; there's a lovely contrast between the unwelcoming established church (apart from the vicar's wife who is a bit more welcoming) and the warm communality of the local Methodists; the climactic moment (spoilers, sorry) is when the narrator finds himself giving an impromptu sermon. The final twist, which I didn't think the film handled very well, is much better in the original. You can get it here.
This was one of the 34 winners of the Guardian Book Prize, which ran from 1965 to 1998. Looking at the list, I think the only other three that I have read are The Condition of Muzak, by Michael Moorcock, Kepler, by John Banville, and Empire of the Sun, by J.G. Ballard.
This was the top unread non-genre fiction book on my shelves. Next on that list is Pigs in Heaven, by Barbara Kingsolver.