Mary Elizabeth and Ewen MacGregor were great.
The person who wrote the TV version did not read the whole book. He missed so many significant details.
First of all, using the book as an opportunity to promote diversity is an insult to diversity and condescending to the book. There were no black Russians in this time period, and not only did the series put them in, the majority of the actors were black! I don't think black actors are so under represented that one has to bend over backwards to put them in. There were no Jews or Muslims as well, because this wasn't their story.
Some of the casting was off. Emile, the chef, in the book, was short, fat and very temperamental. The relationships Rostov had with the kitchen staff, with the American and with the main Russian overseer were not developed enough. These friendships were at the core of who Rostov was and instrumental in Sophia's escape.
Rostov's new room had a window the size of a chessboard, and the roof slanted. He was so tall, that he often bumped his head on the lower part of the slant. You did not see that in the TV series, and the series added a giant window.
Certain quotes the Count made were quoted throughout the book and were important, and only quoted once at the end of the series.
The brightness and the Count's cheerful demeanor, in the book, made the terrible events more powerful, and their introduction is more subtle, making the events more chilling than in the series.
The escape in the end was meant to be surprising and like the pieces of a puzzle fitting together. Throughout the novel certain objects the Count waxes about. These objects are later used in Sophia's escape. His amiable relationships also contributed to the escape.
Movie audiences today are so jaded and so starved for action that I think the producers catered to the public and were in fear of going deeper than they did.
The series was good but nowhere near as good as the masterpiece novel. This TV series was a rushed piece and unfortunately misses too many of the intricacies and cleverness of the novel.
It was a tall order, but it could have been done, as we have seen many tall orders filled in binge series today.
Read the book. You won't be sorry. Every sentence is a jewel.