The War Within These Walls by Aline Sax

This illustrated verse novel has the feel of a memoir.  Misha and his family live in horrific conditions in the Warsaw Ghetto.  Food runs out and death is everywhere.  "It was astonishing how quickly you became used to the smell of starvation and the site of naked corpses."  Misha uses the sewer tunnel system to leave the walled city and search for food.  Janina, his sister joins him, but one day even she doesn't return.  The Germans soon become wise to the system and use a "gruesome" weapon, to send a scorching fireball down the manhole.
Misha connects with a group of resistance fighters who make a stand against the Nazis.  While the story fictionalizes the Warsaw Ghetto Uprising, approximately 750 Jewish fighters fought off over 2000 Nazi soldiers for four desperate weeks.  Read the book and witness what happened to thousands of Jewish people.