The Inner Shrine is probably a decent enough novel in the romance genre, and people who like that sort of thing today will probably enjoy this as well. After an opening couple of chapters in France, where the older heroine's first husband dies in murky circumstances, we then shift to New York, where the challenge becomes to unite three pairs of lovers sundered by circumstance and social codes (all are, or have been, very rich). You probably aren't going to read this, so I shall reveal that the "Inner Shrine" of the title is a woman's heart, which can be unlocked by the three words "I love you." That is probably the crucial data point that will help you decide if you want to read this book or not.
I think I gained also some insight into the strict code of morals of the American east coast aristocracy as it affected my own grandmother, who almost shared a name with the younger heroine of this book (Dorothy rather than Dorothea) and was born into a family of transatlantic steel magnates in Philadlphia in 1899; her uncle became Attorney-General of the United States and her step-brother was a Pulitzer Prize winning literary critic. I knew her, of course, as a crotchety and somewhat snobbish old lady, but it's interesting to get a more direct insight into where that came from.