This thread with /u/restricteddata may be of interest, especially this paragraph:

In general, the Stone/Kuznik stuff has the sniff of late 1980s/early 1990s leftist "revisionist" scholarship to it. It isn't the worst, and some of those points are worth making. But it is not representative of what most historians think about this stuff, which, again, is somewhere more in the "center" than either the "revisionist" vs. "orthodox" approaches these days. It turns out history is super complicated and its hard to make it support one political ideology or another. On the whole, it feels a little outdated — the historical community has already spent 20 years going over this stuff and getting out of it anything that had value and integrating it into a more nuanced model of the end of World War II and the Cold War.

/u/restricteddata also looks at a different claim here about if Reagan turned down a treaty with Gorbachev, and /u/Georgy_K_Zhukov and restricteddata team up on this question on if Truman had "gender identity" issues.

Having said all that, there are many claims being made not included in the answers above, so more answers are welcome. It may help to ask about a specific claim you're wondering about, since not everyone has had time to watch the series or read the book.