Lora Palmer's The Mirror Masters focuses on the tale of Leah Ellis, a girl who was adopted when she was two years old, and later in life starts seeing images in a mirror that she can't explain. Leah learns that she is actually an alien known as a Mirror Master, who can gaze into mirrors to see future events develop and travel through them to other places.
Leah must travel back to her home planet of Jantyr after learning that her birth sister has trigged a device that is setting off natural disasters there. She joins several of her Earth friends and her next-door neighbors -- who are actually aliens from Jantyr who know about Leah's past -- to stop her sister, before events lead to not only the destruction of Jantyr but the entire galaxy.
The book's biggest strength is the main character, Leah. She is a complex character who values her family and friends and will do whatever is necessary to help them. She also admits to her fears about what she must do, but finds the courage to do so knowing so much hangs in the balance.
Palmer also does a great job with world building. You get a good picture about not only the Earth community in which Leah grew up, but her birth world of Jantyr. The latter is particularly where you get a good idea about what the world is like, given the number of locations that Leah and her friends explore.
The biggest issue I had was that the story wrapped up too quickly -- the climax is abrupt, in which you have a lot of tension built, but events get resolved without much reflection about what happened and the ramifications for what may come next.
That aside, I enjoyed The Mirror Masters and consider it a recommended read. It is available on Amazon.