The Children Of Dynmouth by William Trevor.
We're in the sleepy Dorset village of Dynmouth, where all seems nice and placid and normal. Almost too nice and placid and normal.....when awkward teenager Timothy Gedge hatches a plan to steal the show at the annual seaside talent contest, and decides to acquire the props he needs from various members of the local community, his blunt persistence and prurient curiosity reveal secrets that had previously been hidden.
There's the local vicar Mr. Featherstone and his wife, who's just had a miscarriage, Mr. and Mrs. Dass, whose son left the village in mysterious and never-spoken-of circumstances, Mr. Plant the local handyman, who despite being a pretty unprepossessing character seems to have been putting it about a bit among the local women, including Timothy's mother, and Commander Abigail and his penchant for bracing early-morning dips in the sea and perhaps just a little too close an interest in the boys of the local scout troop. And then there's Kate and Stephen, two younger children whose respective mother and father have just married each other and are away on their honeymoon, Stephen's mother having died after throwing herself off the cliffs near Dynmouth. Or was there something more sinister to it than that? Timothy seems to think so.
Gradually Timothy builds up his set of props for the show while sowing fear and confusion in the local community, so much so that eventually Mr. Featherstone takes it upon himself to intervene, though in a typically mild and British sort of way.
And that's about it - all done and dusted in about 190 pages, no shootings or beheadings or car chases or anything, lots of talk and acute observation of social awkwardness, in particular that peculiarly British sort of desperate avoidance of anything resembling confrontations or emotional outbursts. Timothy clearly suffers from some sort of what would now be called an autism-spectrum disorder (and would have been known in the 1970s as just "being a bit odd"), exacerbated by his unfortunate upbringing - absent father, shiftless mother and older sister, neither of whom were too fussy about shutting or locking the door when they were having it away with a series of random men on the living room carpet. We're invited to consider the same nature/nurture questions as we were by We Need To Talk About Kevin, though that book stacked the deck slightly by portraying Kevin's upbringing as pretty normal and stable (plus, to be fair, Timothy hasn't actually murdered anybody yet).
In a lot of ways William Trevor is a sort of male equivalent of the Penelope Fitzgerald/Beryl Bainbridge/Muriel Spark school of dark little fables I've alluded to a couple of times before. The other book of his I've read, Felicia's Journey, conforms to the same sort of pattern and was filmed in 1999. IMDB reckons The Children Of Dynmouth was adapted for a Screen Two presentation in 1987 as well.
Now the awards bit: The Children Of Dynmouth won the Whitbread Prize (now the Costa Award) in 1976 (as did Felicia's Journey in 1994), so you can add 1976 to the list given here.