Given the age of the book, you probably know the story, Sir Percy is the Pimpernel and he and Marguerite are embroiled in a plot by the French Committee. The novel is told from Marguerite's perspective and features a lot less "action" than any television or film adaptation. The important part here is not how the story is told, but the ways in which it is told. Marguerite is married to Sir Percy, but loves the Scarlet Pimpernel, sound familiar? Jane Foster wants to make time with Thor but ignores Donald Blake? Diane Meade is fascinated by The Martian Manhunter, but doesn't care for Detective John Jones? Videl is obsessed with uncovering the true identity of the Great Saiyaman but finds Gohan forgettable? Shove that in your pipe and smoke it misogynist idiots who say women have no place writing superheroes, a woman invented one of the major tropes that can be found in just about every comic, film or television programme in the genre! Also, No one suspects that Sir Percy could possibly be the brave, intelligent and resourceful Pimpernel, because he's clearly a useless dandy. I mean, there's no way the party-boy Bruce Wayne could be Batman right?
So yeah, the book is a pretty fantastic meta-text. It's not a great read to be honest, the language is repetitive and the narrative is predictable, but that's not what makes it such a classic. The Pimpernel is the precursor of Zorro, the Spirit, Batman, Green Hornet, the Lone Ranger, Blue Beetle, the Great Saiyaman, Martain Manhunter, Superman and countless others. If you're serious about seeing where everything from Golden Age Batman to Captain America: Civil War evolved from, you need to start here. Perhaps not the best work in the genre, but certainly one of the most important. "They seek him here, they seek him there..."