The Elsewhen Gene by Gary Bullock
Laura Elizabeth Austin grows up in a small farming town in Kansas. Already a genius at age eight, she and equally bright Elijah Lucas Grant are very different from other kids, but Laura and Elijah have each other.
Fascinated with science, they seriously discuss the big cosmological questions – the nature of time, black holes, the origin and the destiny of the universe, so the two little prodigies become soul-mates, at the tender age of 8.
At the age of 12, on a bicycle ride together, they have their first kiss while debating the nature of time. (Laura claims it doesn’t exist. She may be right.)
They are also troubled by strange visions. Laura sees people who aren’t there. She thinks they are ghosts, but comes to realize that they exist in another universe, and think that she is a ghost. She discovers that she can actually step into an alternate universe, which leads her to believe that this ability is embedded somewhere in her DNA.
Elijah sees flashes of events that haven’t happened – yet. But he learns to develop this into an unerring sense of the future. As the Red Queen says, “It’s a poor memory that only works backwards.”
To put it simply, Elijah sees time forward and back; Laura from side to side.
They soon learn the future isn’t what it used to be. Neither is the past. But in the eternal present, they have each other, for now.
Together they embark upon an adventure across multiple universes and alternate lives, saving themselves from a stampeding buffalo herd, a sadistic security agent, and a cosmic Apocalypse.
Also, while working for their PhD’s at the prestigious MIT, they help to reunite a World War 2 fighter pilot, stranded in the wrong universe, with the love of his life, who is trapped in another. All in a day’s work.