Does anyone know what book this is?

Okay so its this boy who walks into a big light. It takes him into the future, but it doesnt look like the future. It looks like a different planet. He fights a wild boar and lives in a tree and stuff. Then eventually he finds these people living there and talks to them and there is a whole fiasco and stuff. Then one of the people shows him a shard of glass that says "Coca-Cola Company" on it and he realizes he is in the future. Everyone in the past died from a disease and stuff. I dont remember which book I read this in but it was a while ago and I want to read it again.

On the cover there was a big blueish white beam and it reached the ground. Please help!