The couple are believed to have paid more than pounds 100,000 for the beachside house on the Isle of Barra in the Outer Hebrides.
Mr Howard is the great nephew of the famous Scottish author and enjoyed family holidays there as a boy.
Sir Compton built the single- storey house in 1934 on a spot that commands panoramic sea views, but for the past 40 years it has been used as part of a shell- crushing factory supplying aggregate for the construction trade.
The house, Suidheachan, near Castlebay, is opposite the tiny island of Eriskay where the SS Politician sank in 1941 with a massive cargo of whisky, most of which found its way into islanders' homes.
Sir Compton began his account of the hilarious after-effects of the sinking in the house, and his novel, Whisky Galore, later made into a film, was first published in 1947.
The house, which was registered as a place of special historical interest in 1987, was where Sir Compton completed other best sellers including The Monarch of the Glen, Keep the Home Guard Turning and Hunting the Fairies.
Retired Barra postman Niall Machpherson who remembers Sir Compton said: "I am very glad that Alan and Sally have bought the house. It is part of their family history and it is such a beautiful spot"
Now Mr Howard and his wife, who received a reputed million dollars for her first novel Destiny, have applied to the Western Isles Council for permission to demolish the factory and extend the house.Reuse content