Thoughts: This is the third book on the Children's Book Council short list for older readers.
I found this to be very reminiscent of John Marsden's Tomorrow When The War Began. Similar as there is a group of teenagers split, for various reasons, from adults, who need to work out how to survive on their own. However, this time, instead of an invasion and a enemy to fight, there is an accident induced nuclear winter and the enemy is the cold, lack of resources and possibly your own government.
The main character, Fin, seems wise beyond his years, but them I suppose becoming solely responsible for your younger brother in a disaster situation may make you grow up fast! Zorn does a great job in portraying him as outwardly calm, but lets the reader see the underlying fear, worry and uncertainty that Fin feels.
The Sky so Heavy also raised many questions about what could happen to society in a situation such as this. Possibly the scariest thing is the scenario she has created is not beyond the realms of possibility. It is also possible to draw parallels to many issues in society today. Shutting people out for to provide "security" for a few, people outside the borders refugees fleeing a dangerous and untenable situation, border control, "illegals" within the boundaries and who has the right to decide who has access to safety and resources and who doesn't. Issues that become a lot closer to home when it happens to citizens within your own country.
Just like Wildlife and Fairytales for Wilde Girls this is a strong story that deserves it's place on the short list. I'm sure this is not the last we'll see of Fin, Lucy and Max.