the best account I have seen is the film: "The Sorrow and the Pity." I it was released about 1970.
The brilliance of the film is in part because it talks to people from all walks of life. From a rich guy who served in a german division, to members of the resistance to ordinary people.
The Nazi's encouraged people to rat out their neighbors if they were jews or whatever. This went on a lot even among professionals. The arts and cinema went downhill, these were mainly nazi propaganda pieces. So you went to theatre to see a movie about the shabbiness of jews and stuff like this.
Hitler issued some order that German men should not have sex with the french but of course this still went on. There was a lot of collaboration with the germans, and a strong minority that formed the resistance. A lot of people on the fringes of society: criminals, communists, socialists etc joined up with resistance so it was a really fragmented group.
And a lot of people just tried to get a long. One guy they interviewed took an ad in the newspaper to say that he had served loyally in WW i and despite his name, he was not a jew. This is how scary it go.
Go see the movie.