Probably "The Hoax of the Twentieth Century", by Arthur Butz, 1974 I think, would be the best single book. The writing is a bit thick, and I haven't actually read it through yet myself, but it's the one that really catalyzed the Holocaust Revisionist movement in the later 1970s.

From 1979 to the early 1990s, he and other Holocaust skeptics held annual conferences to present scholarly talks that were then published in their "Journal of Historical Review". I was following the issue closely at the time, and read most of their articles, if not all of their books. I remember that Butz won my respect for being a stickler on adhering to scholarly ethics and caution.

The field is wide, and a significant literature was published during that time, of varying quality, much of it apparently quite good. Of course, they were black-balled from the beginning, so they were deprived of the benefit of honest engagement and peer review from professional historians. As I recall, though, virtually all of their books and papers contained plentiful citation, and normally analyzed their data to make an argument.