I read quite a bit of “The Gulag Archipelago” by Aleksander Solzhenitsyn about the forced labor camps in the old Soviet Union. Like you, after a while, I had to just close the book and put it away for a couple of years. Informative, gripping but unrelentingly grim.
The same can be said of certain parts of War & Peace by Tolstoy. War & Peace has increased value as a record of history, one often observed from a point of detachment.
While visiting my parents years ago, I stayed up all night reading “One Day In the Life of Ivan Denisovich”, could not close it up. Read about half of Gulag but visit didn’t last long enough. I just bought it for about $1 on Amazon so I can finally finish it.
Tolstoy didn’t witness the Napoleonic wars...
Tolstoy died in 1910 so he would not have been old enough to remember or born at that time...