First of all, The Scarlet Pimpernel is one of my favorite story lines of all times. As a novel it could be a tad tedious, but I think I've watched every movie rendition that was ever made. So when the author says that she modeled The Forbidden Lady after The Scarlet Pimpernel, I admit I am predisposed to like a story.
If you've never read a historical romance this would be a good one to start with. I don't think historical is this author's primary genre, so she writes with a more characteristically modern feel. To me, The Forbidden Lady combines the "perkiness" of a typical regency but with a little more rational thought. (I can't be the only one who thinks the English aristocracy of the 19th century had to be one of the most contrived societies in history.)
I also loved how she wove historical events like the Boston Massacre into the story. Some of you who are sticklers for historical accuracy might need to curb your instincts. I didn't bother mapping out the timeline to assess the accuracy of every detail, but the language is clearly more modern. Not sure when "oops" was first used, but pretty sure it was sometime after 1775. Plus, some of the humor relies on sexual innuendo that requires an understanding of fairly modern colloquialisms. That did not affect my appreciation of the story or the author's style at all.
I would classify the heat level as spicy. There are some fairly explicit scenes, but they don't drag on and on, and the emphasis remains on the relationship between the hero and heroine. All in all, I would say this one is definitely worth reading.