I put some of my favorites:
-City of God- Saint Augustine
-Rome History- Indro Montanelli
-A Study of History- Arnold Joseph Toynbee
-Histories- Herodotus
-Mister Inquisitor- Julio Caro Baroja
-Castaways- Alvar Nuñez Cabeza de Vaca
-The True History of The Conquest of New Spain -Bernal Diaz del Castillo
-The Roman Republic- Isaac Asimov
About Hitler, it's best to read Hitler directly, his two books are: Mein Kampf and Zweites Buch. Both can be found in English.
You wion't find almost anything of quality written about Hitler, because on the one hand the officialdom refuses to admit that Hitler was a socialist, they want to sell us that he was a capitalist and called himself a socialist to deceive the workers, and since that is the key to understanding why he did what he did, they are unable to explain anything and have to to resort to saying that he was crazy and similar things, when if you understand that he was a socialist, with a socialism based on race instead of social class, everything makes sense and what he did makes sense from that point of view.
On the other hand, the "dissidents" dedicate themselves to inventing reality: Saying that Hitler was a man of peace when he clearly despised them, that he wanted to fight against communism when he clearly says that his interest is expansionism and that communism is a happy coincidence but that he doesn't want to invade Russia just for that, that Hitler invaded the USSR as a "preventive measure" when in Mein Kampf he already explains what he has to it do and why, etc.
The best thing is to read Hitler and so you can see what he really thought and not what the propaganda on one side and the other says about what he thought.
I can recommend a book: Hitler's Beneficiaries- GÖTZ ALY. The book explains how the Third Reich implemented socialist wealth redistribution policies that benefited the German population, thereby winning the support and loyalty of the population.
Once you read Hitler, you simply have to read any book that describes the facts and everything falls into place once you understand how he thought.