The Paris Apartment

 The Paris Apartment by Kelly Bowen 

Lia gets left an apartment from her grandmother, which she had no idea about. When she enters the apartment she realizes there is all of this beautiful art displayed in the home. She contacts Gabriel to help her determine what is real vs. fake, what's actually her grandmothers art and where the rest came from.

Lia and Gabriel undercover some clues where they find out her grandmother was working against the Germans! Gabriel also uncovers that his fathers sister didn't really parish in an explosion, but she made her way to Paris and was working with Lia's grandmother. 

One of the best books I've read this year!