The book is already in stores, in advance of its announced release date. I picked up a copy at a Barnes and Noble in Raleigh, NC, so it can't be too hard to find (unless there is some mystical connection between Moscow and the Triangle area of NC...). I haven't seen the US release yet, but the captioned Russian version of the film that I bought on eBay a year or so ago follows the first 1/3 of the book pretty closely. The translation is nicely done--it's by Andrew Bromfield, who has also done Boris Akunin's "Fandorin" series of mysteries.
The book takes the form of three interrelated episodes. All interesting, but for my money, each ran on too long. I know too little about the Russian publishing industry to hazard any guesses, but a sympathetic editor could have streamlined things a bit. I was also surprised that the novel didn't seem to be terribly "Russian." Of course, there is the whole bureaucratic relationship between good and evil. There is also some mention late in the book of Russia as a young civilization where things are still possibile, and an interesting discussion of the path that Light has followed from the Tsarist through the Socialist eras and into the present, but it seems to be almost an aside.
To return to the idea of the bureaucracies of Light and Darkness, I think that this also serves to dampen the horror. After a while, the struggle between good and evil seems to be about as horrific as a contentious EPA hearing. I suppose that the consequences of this struggle are as terrible as any battle at Carfax Abbey or on a newly-risen R'lyeh; they just don't seem too gripping when they're underway. It's like C-SPAN in Hell.