Gulag: A History of the Soviet Concentration Camps

Extremely thoroughly researched, documented, organized and structured (though I disliked the chosen structure - on themes rather than chronologically, because it leads to reiterations of the same periods).
But dry and often boring, failing to capture the most important element of the Gulag: the scope of individual human suffering, lost here in a too ”from above”, too large and statistical picture.
PS: I recommend you avoid the Penguin Books edition, it is printed in tiny-tiny crowded letters, on very thin paper, with ink that gets on the fingers.