Thanks to BookRiot for naming A Reunion of Ghosts one of The Best Books of 2015 So Far. They say of it:

Mitchell’s novel is an exploration of unintended consequences and the burdens of well-mapped bloodlines, brought together in a perfect confluence of humor and despair. Its narrators are the Alter sisters, three intelligent, tragedy-plagued women bound together by antiquing family regrets and a suicide pact. The book becomes their farewell. They detail generations of family triumphs and mishaps, recalling loves gone awry and lamenting the regrettable best-of-intentions invention that brought Germany one step closer to Zyklon B. Mitchell’s book made me laugh (right before religious services!) and cry, and will remain distinct in my memory as a rare novel that deals with huge historical events–the Holocaust, pogroms–without becoming either tedious or cloying. This novel is a surprise and a treat.

There is also an earlier review, naming Reunion a best book of June 2015 here.