Hinterland

A tear is a little thing. It can start from a frayed thread. Is a tear a rip? Sometimes, a rip can lead to an opening. Sometimes, things can go through that opening. But as things come in, then things can go out. A balance must be maintained.
A group of kids on vacation with their parental units at a bird sanctuary on the US/Mexico border encounter the greatest cataclysm of Earth's history: a rip in the time space continuum. Kids from our time are exchanged with identical kids from another now, where history had gone differently. Balance is threatened and a bunch of kids from there are forced here. Doubles!
A wild, YA/Adult adventure, compulsively readable, funny, challenging, with wacky warps and twists and monsters.