The author you refer to, David Irving, has been totally discredited among his peers, who universally reject his conclusions about the holocaust. Irving is not even allowed to enter the countries of Australia, Canada, Austria, and Germany.
The fool in question claims to offer $15,000 to anyone who can prove it actually happened in the manner that virtually all historians accept, but he will probably not consider any kind of "proof" unless it includes each person's name, address, birth certificates and death certificates showing cause of death of every person killed.
Irving has lost a number of law suits against him for defaming the reputations of real historians. That is why the cash "reward" is so low -- with financial backing from pro arab sources, he can afford to lose often should his requirements for "proof" be rejected in court, plus who would take on the expenses of a law suit for a potential reward of only $15,000?
The man is an utter fool who cannot accept reality. The same applies to those that agree with him.
mlsoft
"As for me and my house, we will serve the Lord" -- Joshua 24:15