The Sealed Letter

I have read about Emma Donoghue, and Room (which my friend Irene told me is the best novel she's read in years).  But this week, I read The Sealed Letter, an earlier novel about a famous 19th century divorce case in London.   It was fantastic.  She is so good about the dynamics of friendship, how far friends can push each other and impose on each other (or not), and why.  I assume that the fact that she's a playwright keeps the forward motion of the story going, and tells us exactly as much as we need to know about the characters.