A truly magnificent achievement. It's one of the few books I started rereading as soon as I finished it.
Trying to explain the structure of this novel is a futile excercise. However, it's three storylines both run in parallel and interact, despite being in totally different eras. This is also a good reason to reread it, since you'll get more out of it the second time around.
The interesting part of the book is that it explores the main themes by the different responses of the characters to their predicaments. Said predicaments being at the same time very similar but also very different. As mentioned, it's hard to explain.
Also props for the flawlessly executed cold open. Very much a risk that rarely pays off but well done here.