A few items of note:
Manlius, ugh. I hated everything about this section, starting off with the name MANLIUS, and it took every ounce of concentration to get through this whole story line. I understand it is important and integral to the story and whatever but whenever I read anything with people talking about philosophy, a little part of me dies. I didn't think Sophia was all that anyway until the end when she owns MANLIUS and completely redeems herself.
I was much more interested in the sections about Olivier and Julien. Though I love any and all story lines set during World War II, Julien's story petered out for me. The whole ending of his story was sort of anticlimactic - but I still was a little sad to see how it all ended. But Olivier - swoon!
I have basically turned this into a harlequin romance but there are definitely Big Questions throughout the parallel story lines which are discussed in considerable detail, e.g., how should we act when our society is crumbling down in pieces before us; is it ever worth sacrificing one life for the greater good; is it better to fight or to accept and try to temper from within, etc. Naturally, I skimmed over these parts.
So, in sum: This book requires great concentration; and it does get annoying how frequently and randomly the viewpoint shifts amongst Manlius, Olivier and Julien; and yes, sometimes you will ask yourself, should I really continue because it is so long and dense, and is the black death really like that? But it is definitely worth it, mostly because we beat the Nazis in the end.