It seems that the definition is unclear. To just say it's a holocaust because a lot of people died is taking away from one some people mean when they say it was a holocaust, as they mean it was deliberate genocide on a large scale.
The Jews were rounded up and systematically...
Does his book state that it was a holocaust?
The total number of deaths is not known (unsurprisingly). The cause of the deaths will vary, as will the intent. I don't think there is consensus on those things. I'm only interested in the truth, nothing else.