Farthing by Jo Walton

In an alternative world of the 1940's, Europe has been taken over by Nazi Germany. England has made peace with Hitler and political control is in the hands of a facist upperclass group that calls itself the Farthing Set. Against this backdrop, Lord and Lady Eversley, members of the Farthing Set, host a weekend party, during which another member of the Farthing Set is murdered. A Star of David has been pinned to his chest and suspicion immediately falls upon David Kahn, the Jewish husband of Lucy Eversley, daughter of Lord and Lady Eversley. Lucy and David realize that he has been set up to take the blame, as does Inspector Carmichael from Scotland Yard. As the Kahn's and Carmichael attempt to find the real killer, it appears that the crime is a political one with huge implications for the future of England.

While not a book about teenagers, and not marketed to teens, this should have cross-over appeal to those look for an engrossing mystery which also provides a lot of food for thought.