Aspects, Bright and Fair

Philadelphia teenager Joni Margulis and her best friend Kelly Grebe don't know where in the world they are. Or even which world. 
Three days ago, Joni convinced Kelly to sneak into her parents' lab and, after fiddling with some suspicious equipment, discovered something astounding: namely, that their world is but one of many, extending in bubbles all around them. Not even Joni's parents know this, but they will in the future, because somehow Joni's dad sent her a transmission across time. And his advice was to run.
Joni and Kelly soon find themselves chased from one exotic world to the next. They steal cars in a futuristic, gang-infested underground city, repel invaders in a tiny medieval-like kingdom, and duck gunfire at a chilidog stand on the Sunset Strip. They meet assassins and spies, earls and innkeepers, many of whom believe that Joni is one of the Cordelians, powerful young women who can see across time. And those who aren't so sure still think it might make the most sense just to kill her.

For fans of Madeline L'Engle's A Wrinkle in Time, Marissa Meyer's Cinder series, or anyone looking for a contemporary sci-fi novel, tinged with fantasy.