Andy--Glad that you are enjoying hearing Drood read aloud. The reader is very good, isn't he? It really does help with the dialogue, causes me to notice things I might read right over. And reader does such a good job presenting the different voices.
I agree that it's probably not the happiest thing in the world to be affianced from birth. No fun and games in finding out who you will marry but instead always knowing--and knowing that the choice has been taken away from you.
Rosa says it well (I find her more approachable if I don't call her Rosa Bud or, worse, Rosebud) in Chapter 3:
"Ah!" cries Rosa, shaking her head and bursting into real tears. "I wish we could be friends! It's because we can't be friends, that we try one another so. I am a young little thing, Eddy, to have an old heartache; but I really, really have, sometimes. Don't be angry. I know you have one yourself, too often. We should both of us have done better, if What is to be had been left What might have been. I am quite a serious little thing now, and not teasing you. Let each of us forbear, this one time, on our own account, and on the other's."
I think of Rosa, so young to be married, so tied to the marriage, so deprived of choice. She knows that Eddy also suffers from the engagement, but he will have a career in Egypt, and she will have only him and the house and presumably children.