Try your local library's catalog search -- using the advanced search you can usually do things like put in 'holocaust' and 'fiction' in the subject and "concentration camp" in the general keywords and get ideas.

For example: http://catalog.mbln.org/ipac20/ipac.jsp?session=A331417664T75.3756&profile=bpl1&page=4&group=0&term=holocaust+fiction&index=.SW&uindex=&oper=and&term=concentration+camp&index=.GW&uindex=&aspect=subtab441&menu=search&ri=5&source=~!horizon&1331417872419