After her friend Vera ghosts her, "aggressively weird" Nephele Weather, 14, begins to obsess over why—whether it's her math obsession or her hirsute Greek heritage—and how to fix it. That's how mathematics ("my one superpower") comes into play. Armed with her knowledge of all things numerical, a strange book found at her parents' bookstore, and her science teacher's assistance, she devises a time travel app named Dirk Angus to change the past. Things, of course, go awry: while Nephele remains the same age, others mature a year every time she goes back, and by her 10th journey, she is no closer to her goal—in fact, that goal has morphed into something new but no less terrifying. Lariviere's (The Bad Kid) YA debut is a multifaceted mélange of math and hormones; Nephele's introspective monologues are filled with elegantly descriptive detail, tending toward a rambling stream-of-consciousness that many readers will find winning.Ages 12–up. Agent: Susan Hawk, Upstart Crow Literary. (Jan.)

Gr 7 Up—Nephele Weather is an oddball, a Greek American high school freshman who is better with math than with people. In school, Nephele is comfortable being invisible, but when her best and only friend, Vera, drops her for stuck-up Ramsey Schultz, Nephele's weirdness seems to be on display. But this child prodigy has a solution: An app that will turn back time for a freshman year do-over. The app works, and Nephele finds herself beginning freshman year all over again. The glitch? Everything and everyone else has moved forward in time, and Nephele's presence in their life (while also being in a different time line) creates troubling holes in their memories. Nephele tries to fix the bugs in the app over and over again but makes everything increasingly worse. It's not until her 10th freshmen year that Nephele figures out the problem with the app and the problem with her social skills, and must make a difficult ethical decision about another redo of freshmen year. Time travel books rely on the suspension of disbelief, and this one is no different. If Nephele were a bit less frustrating and her 10th freshman year friends a bit less caricature, the illogical tech wouldn't matter so much. VERDICT Fans of Scott Westerfeld's YA sci-fi and the whimsy of Dr. Who will make allowances for the knots in this time line.—Jennifer Miskec, Longwood Univ., Farmville, VA