At the start of this thought-provoking sci-fi novel, Abby, twelve, is unhappy and pessimistic: she misses her old life in Pennsylvania (her family has moved to Florida's Space Coast for her physicist mom's job) and obsesses about societal and environmental ills. Then she meets Adam and Bix, who tell her they've come "from a long distance away" and are on an urgent mission to find Adam's lost sister, Vanessa; in fact, they're from the twenty-third century. Adam allows Abby a glimpse of that future, a world of "creation, possibility, exploration, and abundance," and Abby instantly decides that she wants to live there. She promises to do all she can to help Adam and Bix if they agree to take her with them when they go. The tension of the boys' quest will keep readers invested (the future isn't totally perfect; if they don't find Vanessa ASAP, an alien pathogen will be released into Earth's population). But Abby's situation is equally engrossing: should she stay, or should she go? She considers all she'd be leaving behind -- friends; family; the community she's just starting to feel at home in; and, most of all, the chance to make a difference in her own time. The twist at the end may not be the most original, but it allows for a happy ending readers will embrace. Martha V. Parravano

Twelve-year-old Abby is full of anxiety about the state of the world.Abby's physicist mother has taken a job at SpaceNow in Florida, and the family has relocated from Pennsylvania, much to Abby's displeasure. Worse, her mother keeps telling Abby to apply herself and look for the positive, and Abby does not feel heard. Then she meets two unusual looking boys: Adam, who is about her age, and Bix, 9. They don't seem to belong to this world-and they don't. As the story unfolds, Abby learns that the two have traveled through a time vortex and need to find Adam's sister, Vanessa, before the future is irrevocably changed. While the premise is intriguing, the novel is occasionally strained in its presentation, with plot devices being introduced that seem to be there simply to get the story from point to point rather than growing it naturally. Abby, who narrates in first-person present tense, has a voice that seesaws among believable snarky tween, some strangely adult-sounding passages, and a detached narratorial voice not unlike a tour guide's. Although readers are told Abby is very smart, there is no evidence of that integrated into the plot, and the same limited characterization is used for her oft-mentioned anxiety, in this case through frequent references to her stomach. While the theme is worthy-don't give up-the delivery is uneven. Abby and her family present White; a prominent secondary character is Latine.A well-intentioned story that doesn't quite deliver. (Science fiction. 9-13)