Are there factual errors in it? I haven't seen any actual valid criticism of the factual content of the book, just "its antisemitic ban it don't let anyone read it!".
I am not saying that the book is not serious. It gives a valuable personal perspective of important historical facts. But it should not be used as a source of factual data.
I think you are confusing him with Putin, who actually said that. He said the cheka was mostly jewish. Which is correct.