And I can't say that the ending disappointed me. Anyone who reads this blog knows that one of my pet peeves is trilogies/series that utilize cliffhanger endings to ensure a readership for the next book. Not so with Tandem. While obviously there's more story to be told, the characters' individual journeys are nicely wrapped up with acts of heroism and sacrifice. I want to read the next book, but I'll be happy in the meantime because the ending here was satisfying. Even though some of the characters (maybe all of them) are still arguably in danger at the end of the book, no one's fingertips are clutching a window ledge (although one character ends up dangling from a rooftop in the middle of the book. Hope that doesn't give too much away.)
I haven't read anything else by Jarzab, but I'm going to remedy that soon She's a confident, daring writer who has managed to contribute something new and different to the YA sci-fi marketplace. Parallel worlds rule! (Anyone remember the TV series, Sliders, BTW?)