The basic plot of 'A Duke To Die For' is akin to that of Georgette Heyer's 'Regency Buck', a young woman finds herself the ward of a titled gentleman and ends up married to him. Of course there are many differences between the two books, not least in the quality of writing and historical accuracy, but 'A Duke To Die For' has some moments of charm.
Henrietta Tweed believes she is under a curse. When her parents died a woman told her that she was cursed to have all her guardians die and that seems to have happened; her father had left a list of six men who could be her guardian until she came of age and when she arrives at the house of the Duke of Blakewell he's the last one on the list, the others having all died once they became her guardian. However, he's not the duke that her father knew but his son, a handsome young man whose rather disorganised life is fairly rakish but mostly harmless.
Blake doesn't want a ward, particularly one as attractive and appealing as Henrietta. He doesn't believe in her curse, of course, but as he tries to find her a husband and as she helps him with his correspondence, his health and his fear of heights, he begins to wonder if he can let her marry anyone else.
This is very much a simple plot, simply told. There are minimal twists and turns in the stories, few disagreements among the characters and the curse aspect of the plot is resolved in a way which seemed rather too easy to me at the end. Historical accuracy isn't that good in terms of dialogue although some of the background information about ballooning was interesting, although that aspect of the story wasn't resolved in this book (there are two more novels planned, about Blake's cousins, which may continue the theme). Although both Blake and Henrietta were very appealing characters, Blake's behaviour as a guardian was pretty dodgy towards his ward and her tumbling into love with him seemed to reach a great depth very quickly.
I abandoned this book part way through. Neither the story line, nor the characters' behaviour really made sense in the supposed context. Also the characters did not come to life as "real" people, but instead seemed rather like cardboard cut-outs. So, unable to get engaged with the story and bored, I gave up.