Looking at the Moon — Kit Pearson

Norah, an English "war guest" living with the wealthy Ogilvie family in Toronto, can hardly wait for August. She'll spend it at the Ogilvie's lavish cottage in Muskoka -- a whole month of freedom, swimming, adventures with her "cousins"...
But this isn't an ordinary summer. It's 1943, and the war is still going on. Sometimes Norah can't even remember what her parents look like -- she hasn't seen them in three years. And she has turned thirteen, which means life seems to be getting more complicated.

Then a distant Ogilvie cousin, Andrew, arrives. He is nineteen, handsome, intelligent, and Norah thinks she may be falling in love for the first time. But Andrew has his own problems: he doesn't want to fight in the war, and yet he knows it's what his family and friends expect of him.

What the two of them learn from each other makes for a gentle, moving story, the second book in a trilogy that began with the award-winning The Sky Is Falling.