Contemporary review from an unknown newspaper, discovered by Peter Thackeray tucked away inside a first edition of the novel:

MR. BUCHAN’S LATEST ROMANCE
This story shows us Mr Buchan engaged in turning over and recombining into fresh groupings a heap of more or less familiar romantic ‘properties’. His setting is the Scottish seacoast, and an untenanted mansion, in charge of a crew of surly, furtive lodgekeepers, who have something to hide, and betray the fact; and of a rough inn-keeper, who is desperately anxious to dissuade travellers from staying at his house.
They work under the direction of one Loudon, a factor, and a bluff, hearty, weather-tanned fellow, who makes the pleasantest impression of a wholesome open-air sportsman, till at length, we are allowed to detect in him just a fugitive gleam of something faintly suspicious. Loudon is good, in the traditional manner. There is a Danish brig, and a landing by a boat’s crew of villains by night, and in stormy weather. There is, inevitably, a beautiful foreign girl, suitably provided with unscrupulous enemies, and with an unwelcome lover, ‘beautiful as a devil,’ who will stick at nothing. For the necessary contrast of the prosaic with the picturesque there is a middle-aged and wealthy Glasgow grocer, timid and respectable by habit, though a stout-hearted fellow at bottom, who has sold his business and blunders into this whirl of picturesque violence at the bidding of a life-long passion for romance, which his retirement has set him free at last to indulge.
Dickson McCunn has many engaging qualities besides his simplicity and kindliness. He has a harmless vanity which makes him thrill with pride when he over hears praises of ‘D McCunn, the great provision merchant’, a praiseworthy habit of carrying Izaak Walton in his pocket when he goes on pilgrimage, and an invincible belief that what is needed to defeat the lovely foreigner’s enemies is the ‘sound business head’ which has brought him his prosperity and modest fame.
As a piquant novelty Mr Buchan has hit upon the device of introducing a band of ragged Glasgow lads, formed into an unofficial body of boy scouts. In the exuberance of their youth, they march to such songs as ‘Class-conscious are we, and class-conscious wull be, Till our fit’s on the neck of the Boorjoyzee’, learned by one of their members at a Socialist Sunday school. But these are battle hymns, sung for the sake of their rhythm, without regard to their meaning, and the boys are unreservedly, not to say violently, on the side of law and order. They are amusing; but we wish Mr. Buchan could have made his villains anything but Bolshevists. The Bolshevist crops up in every shocker nowadays; but for romantic value he is, say, to the old-fashioned pirate, as a penny is to a pound. His associations are not picturesque at all, but merely ugly, and as a figure of romance he stands far below even the nihilist of a generation ago, who figured bravely enough in many of the older stories.

Audio version, LibriVox: https://archive.org/details/huntingtower_1205_librivox/huntingtower_01_buchan.mp3