This is not fluff. It seems like fluff and I have read lots of fluff by this author, but this particular book is not. I feel like this book will appeal to a wider audience of teen and adult readers than Regency Romance usually does. And it helps that it is only 190 pages and has an absolutely fabulous and fearless main female character with a backbone on steel. (That's as much of a spoiler as you are going to get from me.) 
 Lord Havercroft and Mr Mason have been neighbors for more than thirty years and hated each other for pretty much all of it. They fit nicely into the stereotypes of impoverished, blue-blood, member of the ton and new money, coal mining, business man. After Lord Havercoft's daughter, Annabelle, ruins her reputation by attempting to run away with a handsome coachman, condeming her family to financial ruin in the process, Mr Mason offers salvation for the price of Lady Annabelle as a bride for his son, Reginald Mason. Did you follow that? 
 Reading Challenge: stolen kiss