How could this be is a classic? It's rotten.

This book is terrible. The author continually describes unimportant clothing, and beats the reader over the head with how smart Marguerite Blakney is, but has her act stupidly. Her life is a complete contradiction. The author writes that Blakney is a republican despises class, but she delights at giving ordering to those around her and thinks nothing of vain displays of her wealth that could only be afforded by an outrageously wealthy person. How unconscious the author is of this.
It appears the author tried to make the "evil" Frenchman like Javert from Les Miserables, but he lacks Javert's depth. If he was so terrible and would go to any means as he said to M. Blakney at the inn, he would have beaten the identity of the Scarlet Pimpernel out of the Sir Andrew when Andrew was first captured. The author also has difficulty with creating behavior with any semblance of reality of most other men.
It reads like a beach romance novel.