A prolific Australian writer of 1960s pulp, specialising in World War II exploitation novels, John Slater is chiefly remembered for the extraordinary cover art (which generally bore no resemblance at all to the contents of his books). The following scans are courtesy of Warrigal Press an online bookstore that is well worth your attention.
I haven't read any of these books, but you may wish to read my comments on Buchenwald Hell, which I have.

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Camp of Terror
Lois' resistance to the brutal Japanese gradually weakened under the strain of the bestial inquisition.

Death Island
The Japanese were masters at the art of cruelty and torture.

Blood Island
A lone white woman is the prize in a grim struggle between Japanese and German troops on a small island outpost.

Sin Camp
Inside a notorious prison camp where white women were made the unwilling playthings of their Japanese captors.

Two For Auschwitz
Inside the notorious concentration camp captive women were made the unwilling playthings of their German captors.