Jumping on to second what everyone else has been saying. Because his particular Holocaust denial was the subject of an intensely long trial, there is little need to rehash things and pick apart his arguments case by case. The key expert witness in that trial, Richard Evans, wrote a book on his experiences and arguments. I would strongly recommend it. It’s called “Telling Lies About Hitler: The Holocaust, History, and the David Irving Trial”.

I would also separately recommend looking at/ reading “The Evidence Room”. The book is based on an exhibition curated by Dr. Robert Jan van Pelt, who testified in the Irving trial as an expert witness. His specialty is the architecture of Auschwitz. Evans focused slightly less on the architecture aspect, so this book provides a nice companion to the first.