Make sure the name of the book is either deep, witty, or generally confusing (or all of the above), while the cover of the book should have anything from a Union Jack, to a concrete jungle, to a King Charles spaniel. Of course there is always the silhouetted man against the city approach. You will need a thought-provoking quote or line somewhere on the cover.
The traditional characters of a book about England would be: A tall man in an elegant suit or tuxedo 24/7; a detective who never goes anywhere without his pipe; a troubled old man with a felt cap and a woolen coat. No matter the character, they must curse and drink a lot to be more authentic.
Content depends on whereabouts you would like to set your book. In London, moustaches, top hats, pipes, and monocles should be included with major roles. In the country, farmhouses, sheep, and sheepdogs are all advised to be included in the story. However tea and biscuits should always be acknowledged.
The storyline must be dramatic and dark with many plot twists and alternate paths.