This collection is a bit hard to categorize. They are generally all told in the first person and so are recountings of those who actually witness what they claim have witnessed. They are bring up questions as to whether or not the person speaking ever witnessed anything of the kind but is rather making it up as they go along.
For what it is worth, read them for what they are worth. They support the things that the writers have revised out of the Holocaust.
If you trust the memory of witnesses you have to read this article.
AUSCHWITZ: A Doctor's Eyewitness Account, by Dr. Miklos Nyiszli
The Trial of the Executioner of Sobibor
The strange Case of Mobile Gassing
Something similar from Vietnam
A witness to six gassings, all his own