Jo Baker did an admirable job describing the life and work of servants. They are treated like carriage horses. They are beasts of burden. They are fed and housed so they are strong enough to work. And work they do, in all weather and at any and all times.
The servants in Longbourn are not mistreated as long as they do their work. When they lose their usefulness they may be sent to the poorhouse (glue factory)or sent to another estate (sold or lent). Pregnant carriage horses are inconvenient. Pure breeds are valuable, mixed breeds are not. There's always a driver with a whip.
The tie in to Pride and Prejudice is unnecessary. This could have been a historical fiction on its own. As far as Sarah, the main character is concerned, Jane is the nicest of the Bennet girls, but neither Sarah nor Baker show that Jane is. Wickham is even wickeder in Longbourn than in P & P and Mr. Bennet is a bit more self serving.
There is a bit of sympathy for Mrs. B. I don't think this enhanced my understanding of P & P. It just made me dislike all of the Bennet's . That probably isn't the purpose.
I would have preferred this if it took place in the same town, same time, just a different, unknown household.(less)