Where to begin?
This is an enormous, serious novel. If you are interested by the history of the first half of the 20th Century (as I am), a fan of the music of Dimitri Shostakovich (as I am), and a lover of literary fiction (as I am) the this book is tailor-made for you. If you are none of those things, you should perhaps approach with caution.
Vollmann has taken a number of 20th Century lives (notably Shostakovich, the defeated Stalingrad general Paulus, the turncoat Russian Vlasov, the well-intentioned SS man Kurt Gerstein, and many others) and woven them into a fictionalised saga to explore the moral maze of Hitler's and Stalin's Europe.
But this is no airport novel. The writing style changes frequently, sometimes spare and straightforward, sometimes outrageously experimental, echoing the music of Shostakovich whose role - in what Vollmann calls "an imaginary love triangle" - is the heart and soul of the book (access to recordings of the symphonies, the cello sonata and the harrowing 8th quartet is highly recommended as an accompanying "soundtrack").
I find it difficult to find suitable comparisons for this book; what it reminded me of most was not literary, but sonic and visual: the aforementioned Shostakovich music, the films of Tarkovsky, the grainy black-and-white images of the 1970s TV series "The World At War". Whatever one tries to compare it to, there is no denying that this evocation of the Berlin-Moscow nightmare world of the 30s, 40s and 50s is a remarkable achievement by a young(ish) American writer, whose work I will be exploring further.
The word "masterpiece" is undoubtedly over-used, but I feel it is justified here.