When we're ready for Buchan -- but let's not get too many irons in the fire! (bad taste allusion to the Kipling story?) -- the stories I'd recommend for consideration would include

A.Short Fiction
The Grove of Ashtaroth
The Outgoing of the Tide
Skule Skerry
The Far Islands
The Wind in the Portico
No-Man's-Land

Those are the stories in the collection of Buchan's tales published by Donald M. Grant in 1984. There are others that would be appropriate, including "The Watcher by the Threshold."

B.Novels
Witch Wood
The Dancing Floor
The Gap in the Curtain