Book - The American Heiress

I'm reading an interesting, light book, An American Heiress by Dorothy Eden. The  illegitimate dgt of a wealthy New Yorker is left with his widow by the house servant  mother. The child grew up to become the maid of the legtimate dgt, but also  educated with her. As adults the legtimate dgt is engaged to an English lord who  needs her money to keep his estate operating. She and her step-sister and mother  sail on the Luisitania to the wedding in England!!! Yes! Hettie,  the "maid", survives, the mother and fiancee die. The mother in an  attempt to save her jewelry had made Hettie wear some of it when they were  forced to abandon ship. When Hettie was found alive she was mistaken for the  bride-to-be. She follows thru and marries the lord, who had only met the  bride-to-be one brief time. It sounds like a stupid scenario, but Eden makes it seem  plausible. The lord marries and hurries off to the trenches in WWI, Hettie takes  control of her "inheritance", which you could say she rightly deserves being the  other spawn of the father, and efficently and soundly uses it to fix up the estate.  There is a woman who anticipated being the wife of the lord but had no money who  is obviously going to be a problem. Also sounds silly, but i'm enjoying it. I know that somewhere down the years she's going to get "caught." that's the  suspense.  Why do we love these upper/lower class relationship stories? Upstairs/Downstairs,  Downton Abbey. Is it just English stories we like. Is there a lower class in The Great  Gatsby? I've forgotten. I'll be curious to see other reviews of this book to see how They respond to Hettie's deception.