What is the author's style in The Thirty-Nine Steps by John Buchan?

Language used in the book, with the majority provided in the first-person, is that of an upper-class member of the United Kingdom around the turn of the 20th century. Vocabulary is advanced, tone is intimate but polite, and sentence structure is measured and elegant. These traits aid in the characterization of Richard Hannay as a man "cool under pressure," and possessive of the famous British "stiff upper lip."