Suggested level: Level 3

The road by Cormac McCarthy. A father and his son walk alone through burned America. Nothing moves in the ravaged landscape save the ash on the wind. It is cold enough to crack stones, and when the snow falls it is gray. The sky is dark. Their destination is the coast, although they don't know what, if anything, awaits them there. They have nothing; just a pistol to defend themselves against the lawless bands that stalk the road, the clothes they are wearing, a cart of scavenged food--and each other. 

Z for Zachariah by Robert O'Brien (might be a bit young though). 

On the beach by Nevil Shute

How I live now by Meg Rosoff. (might scrape through the reading level). To get away from her pregnant stepmother in New York City, fifteen-year-old Daisy goes to England to stay with her aunt and cousins, with whom she instantly bonds, but soon war breaks out and rips apart the family while devastating the land. Suggested level: senior secondary. 

The knife of never letting go by Patrick Ness. Todd Hewitt is just one month away from the birthday that will make him a man. But his town has been keeping secrets from him. Secrets that are going to force him to run. 

Life as we knew it by Susan Beth Pfeffer. Through journal entries sixteen-year-old Miranda describes her family's struggle to survive after a meteor hits the moon, causing worldwide tsunamis, earthquakes, and volcanic eruptions. 

The dead and the gone by Susan Beth Pfeffer. With haunting themes of family, faith, personal change, and courage, this powerful novel--a companion to "Life As We Knew It"--explores how a young man takes on unimaginable responsibilities.

Kokopu dreams by Chris Baker. "Before the telly died, haggard looking people, politicians mostly, described how an illegally imported rabbit calicivirus had mutated. It wasn't killing rabbits any more, and nor was it affecting cats and dogs, and not the native bat nor the little spotted kiwi. But it had been killing people with a type of haemorrhagic fever that travelled from the Mackenzie Country up and down the land like the wind, from Bluff to Cape Reinga in about three weeks. And that was the good news"--Back cover.

Genesis by Bernard Beckett. Now we are alone. Outsiders can no longer be trusted and are shot on sight. Here in the new Republic the people serve the State and the Philosophers who guide it. Until one man, Adam Forde puts himself at grave risk, and changes everything.

The Obernewtyn Chronicles by Isobelle Carmody

The sea-wreck stranger by Anna Mackenzie. Ness, Ty and their cousin Sophie live in a post-apocalyptic island community that has turned its back on the sea, and its own past. When the arrival of a stranger forces all three to question the world they know, a world dominated by superstition, fear and loss, they each have a choice to make. Rebelling against the harsh austerity of her life, Ness chooses to follow the sea currents running in her blood. It proves a choice that risks everything, including her own life. Suggested level: secondary.

Bloodline by Michael Grant or any others along this line.