Honestly, I didn't like the book while I was reading it.
It was only after reading it and reflecting on it that I started realizing how well crafted it was. It is certainly not a plot driven book or even a character driven book; it is more about themes and ideas.

Time, memory, remembering and being remembered (remembrance) are important - to what extent can we remember, how do we remember, what do we remember. Over time history becomes overlaid with other histories - Napoleon war, WWI, WWII - with time these huge events become increasingly forgotten.

How do we remember - stories, pictures, places, museums, libraries - but as the novel goes on these become increasing difficult to access - the library is guarded by librarians, the museum by hours and glass barriers, photos by those unidentified in them. Layers of strata as buildings are built over rubble, over graves, over the past. New architectural structures combine with old architectural structures. Time passes yet clocks are broken, memory breaks from the present to the past, today's train ride echos earlier train rides. City walls become fortresses become concentration camps become museums. Much remains the same but also changes.

Layers seem to be a primary theme - layers of narrators "'he said, she said' he said." Layers of memory, layers of history, layers of places.

Much of these themes and ideas would become clearer and perhaps even brilliant upon a second reading but, sigh, there are other books I want to read.