This is book three in the "Knickerbocker" series, which is a series set in the Gilded Age following sequentially the various members of the "Knickerbocker Club," an alliance of businessmen who don't like each other but are determined to put that aside to commit insider trading, because it hasn't been outlawed yet. It is billed as book two but it is actually book three, because book one was a novella and that makes it only half a book, so it didn't count as book one in the official numeration of these books, because reasons. This is standard romance publishing industry fuzzy math, okay? Book "two" focuses on Knickerbocker #3, who is a railroad baron, and his forbidden whirlwind romance with a woman who dresses up as a Russian and performs fake seances for rich folks. Which is a fun set up.
I have read both book one and book zero-point-five and now book two, and I still can't totally tell you why I'm so keen on this series. Between the three books, I've found the interpretation of the Gilded Age to be Problematic, with labor-abuse apologetics paired with an understanding of turn-of-the-century American business practices that seems to be based entirely on "beating Carnegie", and a lack of nods to certain things of the era I'd expect, like the Progressive movement. Being a bit of a socialist I sadistically envision the epilogue in a couple of decades when the Knickerbocker heroes in this series all totally eat shit on Black Tuesday, like Caledon Hockley in Titanic. And, a more salient criticism for readers of such things, the plots tend toward distracting artificial tension and subplots featuring secrets, misunderstandings, secret misunderstandings, and blackmail. The sex scenes are excessive and repetitive, and pretty historically tone-deaf. (You expect me to believe a hard-boiled socially elite capitalist can look down on a poor woman as unmarriagable AND YET every time they have sex still cheerfully go down on her like a starving truffle pig? I'll try, but...) But this stuff is par for the course in Romancelandia, you check your knowledge of the historical method at the door and hope it'll still talk to you when you stumble out drunk and covered in glitter in a few hours. So I am still cheerfully reading them. I like these books, even though they are objectively not very good.
I think what's appealing to me about these books is that they are a thoroughly American sex-romance fantasy. You look at British set-piece historical romances, they have dukes, marquesses, sometimes mere lords, but the overwhelming majority focus on the sexual fantasy of a fantastically wealthy man with clean hands who smells like bergamot and has ample time to both pet your hair and partake of his favorite leisure activities. In America, of course, titles are illegal, and capitalism is our sacred peerage system. And so, our fantasy of idealized masculinity focuses on Hard Work, and a lot of our masculine sex objects reflect this, with archetypes like Cowboy and Executive. So why not weld up the two fantasies of old-timey-cravat-wearing-rich-dudes and all-American-masculine-sweat-equity with ...robber barons? It's such a fantastically apropos idea I'm shocked it hasn't been already beaten to death in Romancelandia yet.
In short, if you are a critical reader of genre fiction, this is the historical romance series you've been waiting for since the English lost the Romance Wars. It's the archetypal post-Austen historical, madeover to be truly American. Read it and feel capitalist pride, fellow ugly Americans.