> I think if you try to take everything in his descriptions of the Gulag system as literal fact, you'll find historical discrepancies

What ones stand out for you? I am relatively ignorant on the subject. Your comment stimulated me to google a bit and I came up with this¹ critical (and currently topical) criticism of him for anti-semitism in which he is accused of blaming Jewish people for playing a leading role in the red terror:

His reported self defense included a reference to the Kiev/Kyiv Cheka (precursors to OGPU and NKVD): 'To explain the actions of the Kiev cheka [secret police] only by the fact that two thirds were Jews, is certainly incorrect."'

1. https://www.theguardian.com/world/2003/jan/25/russia.books