I've recently reviewed the young adult book, The Vanishing of Katharina Linden by Helen Grant, on my other blog.
Though the protagonist is only 10/11 at the time of the events that occur, it is her older 17/18 year-old self recounting events.
It's a crime novel, set in Germany and if you liked the chapters narrated by ten-year-old Kate Meaney in Catherine O Flynn's What Was Lost, you will probably enjoy this one.
I certainly did and found it to be well written with an engaging lead and the German traditions added to the interest.
My review can be found here.