Published by Polands Ministry of Information in 1942, this English language book details Nazi atrocities in Poland between September 1939 and June 1941. Naturally this was compiled by the Polish government in exile as Poland was occupied at the time, but there was quite a lot of information flowing from the Polish underground to the Polish government in London.
It's very detailed and every page (there are 600 of them) lists numerous atrocities committed against both individuals and groups. Murder, mass murder, slavery, rape, theft, forced migrations, kidnappings, cultural icons destroyed or stolen, etc., with some specific circumstances being cited that were difficult to read. A sane mind left to wish these stories were made up, or exagerrated only to know that this is rarely the case.
Included in the book are reports/speeches about German atrocities in Poland as reported by Winston Churchill, Vatican Radio and other third party sources.
There are dozens of pages about persecution that Jews suffered (regulations, confiscation, expulsion, ghettos, and massacres/brutality). Similarly dozens of pages on the persecution of the Catholic church as well.
This book took me months to read, partly because I could only stomach reading about the horrors and atrocities in small batches, and party because I kept finding myself diving into rabbit holes of further research (Googling, as one might say), about persons, places and events discussed in the book.
Amongst the surprising parts were the punishment German citizens and ethnic Germans received if they didn't treat the Poles like lesser humans. I loved this tough to find book.