Gordon Korman 

From the author of Restart, the story of two boys who are losing their memories... to each other.

Reef and Theo don't know what's happening to them. They'll be going about their days and then suddenly they'll have these strange flashes of memory -- but the memories don't belong to them. And at the same time, their own memories are starting to... vanish.

For Reef, this is a big problem, because memories are all he has left of his mom.

For Theo, it's strange because the new memories give him a freedom he doesn't have with his domineering dad.