Gaby was living a normal life, working in the local library with her roommate, Maggie, until she found out that she and her recently deceased twin brother, Jude, are actually Rephaimhalf human, half angel. With that revelation, Gaby is thrown into a world of hellion beasts and a history she cannot remember. She also discovers, however, that Jude is alive, and they are reunited. Subsequently, their best friend, Rafa, and another Rephaim, Taya, are captured and imprisoned by Gatekeepers who intend to do them great harm. Gaby, Jude, and some of the Outcasts (a splinter group of Rephaim) have arrived at the Sanctuary (a headquarters of the Rephaim) to plead for help in rescuing Rafa and Taya.As Shimmer is the third installment in The Rephaim series, readers not familiar with the first two books will be somewhat bewildered. The cast of characters is large, and the various relationships are complicated with lots of history. Gaby herself does not remember her life as a Rephaim and struggles to regain some sense of equilibrium and understanding. Nonstop action moves the story along rapidly and keeps readers breathless. Teens who enjoyed Lauren Kate's Fallen series will no doubt find this series appealing. The book does not stand alone but will surely satisfy readers already devoted to the series.Debbie Wenk.