Parallelogram Series by Robin Brande

(Book 1 of 4) NO ONE IS GOING TO BELIEVE ME. High school senior and amateur physicist Audie Masters has discovered what no other physicist has been able to prove: that parallel universes do exist, and there is a way to journey into them. She also discovers something else: a parallel version of herself, living the kind of life Audie never could have imagined for herself.Now Audie is living that life, too, full of adventure, romance, and reality-bending science... more(Book 1 of 4) NO ONE IS GOING TO BELIEVE ME. High school senior and amateur physicist Audie Masters has discovered what no other physicist has been able to prove: that parallel universes do exist, and there is a way to journey into them. She also discovers something else: a parallel version of herself, living the kind of life Audie never could have imagined for herself.Now Audie is living that life, too, full of adventure, romance, and reality-bending science. It’s all more than she could have hoped for—until something goes wrong. less

In a desperate move to save the life of her parallel self, high school science genius Audie Masters managed to bend the laws of physics. But now she's trapped in the wrong universe, with no sign that her scheme to save her alternate self, the famous teenage explorer and adventurer Halli Markham, actually worked. Until she can sort out the physics of what went wrong, Audie has to pretend to be Halli--and fool everyone from Halli's parents to the guy who's in love with her... moreIn a desperate move to save the life of her parallel self, high school science genius Audie Masters managed to bend the laws of physics. But now she's trapped in the wrong universe, with no sign that her scheme to save her alternate self, the famous teenage explorer and adventurer Halli Markham, actually worked. Until she can sort out the physics of what went wrong, Audie has to pretend to be Halli--and fool everyone from Halli's parents to the guy who's in love with her. And meanwhile there's her own life Audie would like to reclaim, including Daniel, the only one who knows the truth about who she really is. Is Halli still alive? If so, where is she? And can Audie ever find her way back to her own universe, her own family--her own life? less

(Book 3 of 4) I NEVER USED TO THINK OF MY LIFE AS DANGEROUS. Halli was used to it--she'd been raised for it. BUT ME?As Audie continues her struggle to return to the right universe and the right body, meanwhile Halli Markham, her adventurous parallel self, must take over the simple, quiet life Audie left behind.Halli has survived the Arctic, the Amazon, and dangers all over the world--But can she handle high school?

(Book 4 of 4) Everything has to change. My life depends on it. High school senior and amateur physicist Audie Masters isn’t simply pursuing science anymore.Her discovery of parallel universes and time travel have now led to a race for Audie to save her own life before it’s too late.From award-winning author Robin Brande comes the exciting, mind-bending conclusion to the Parallelogram series. You’ll never look at the universe or your own life the same way again.