A occult thriller -- homage to the great pulp adventure novels on the 1920s-30s. The Wikipedia entry for "Yellow Peril" says it well:
..."Yellow Peril": The Adventures of Sir John Weymouth-Smythe, by Richard Jaccoma (1978) is both a pastiche and a benign parody of the Sax Rohmer novels. As the title suggests, it's a distillation of the trope, focusing on the psychosexual stereotype of the seductive Asian woman as well that of the ruthless Mongol conqueror that underlies much of supposed threat to Western civilization. Written for a sophisticated modern audience, it uses the traditional use of first-person narrative to portray the nominal hero Sir John Weymouth-Smythe as simultaneously a lecher and a prude, torn between his desires and Victorian sensibilities but unable to acknowledge, much less resolve, his conflicted impulses. The cover blurbs for the paperback edition declaim "Erotic adventure in the style of the original 'pulps'" and "'A Porno-Fairytale-Occult-Thriller!' according to the Village Voice". It is clearly in the same line as the contemporaneous works of Philip José Farmer, "updating" Rohmer the way Farmer updated Edgar Rice Burroughs, Lester Dent, and Walter B. Gibson.