Once Was a Time, by Leila Sales (Chronicle Books, Middle Grade, April 5, 2016).
In England in WW II, Lottie's scientist father spends his days trying to figure out the secrets of time travel. He believes that shimmering time portals randomly appear, but doesn't know how they work. Time travel could have military uses, and so 10-year-old Lottie and her dearest friend Kitty are taken hostage; the kidnappers think her dad knows more than he's letting on, and are going to kill the two girls unless he spills his secretes.
And then a time portal appears (!) and Lottie, hardly pausing to think, jumps through to escape her captors, leaving Kitty behind. And her father, and the whole world of WW II England. She finds herself in our time, in the Midwest, in her pajamas in the middle of nowhere, with no way to get home again. Fortunately, she finds a friendly library (which has relevance to the plot). Fortunately as well, she is taken in by a foster family (child services is almost magically wonderful), and so she becomes an ordinary American school kid. Except that she is haunted not just by her lost life in generally, but by her abandonment of Kitty. Never will she have another friend like her, and so she goes along with the group of girls who took her in, enchanted by her English accent, even though she doesn't have much in common with her.
But then she finds something hidden in a copy of her favorite book that gives her hope that she might find Kitty again, that maybe Kitty didn't die, even though that's what it says on line. And so she finds a way to get to Italy, with the help of a boy who could have been her friend if her clique of girls hadn't taught her to shun him, following clues that Kitty maybe, perhaps, left.....
This is both a good, solid time travel story (by which I mean it deals with the whole cultural dislocation of time travel nicely, without getting too terribly caught up in Lottie's exploration of the wonders of the future), mixed with a good friendship story--being true to yourself and making friends with who you want to be friends with without getting caught up in peer pressure. The best part of the book was when Lottie and the shuned boy who is now her friend get to know and appreciate each other, and Lottie starts realizing that even though she left Kitty that doesn't mean she shouldn't ever be allowed to have good friends again.
So if you go to Amazon you'll see that there are people saying this will appeal to fans of When You Reach Me and Wrinkle in Time. Um, not so much, I think, especially not Wrinkle in Time which is not actually about time travel qua time travel for crying out loud. And When You Reach Me feels like it has sharper edges than this one. I think it will really appeal to fans of Charlotte Sometimes, by Penelope Farmer, which probably hasn't be read by young people today....to me, a fan of older English books like that one, it had a lovely familiar feel and I enjoyed it very much. A contemporary review of Charlotte Sometimes said ""…this is really a study in disintegration, the study of a girl finding an identity by losing it… " and this is exactly what happens to the Charlotte of Once Was a Time as well.
It also reminded me of Dreamer, Wisher, Liar, by Clarise Mericle Harper. But even if you don't like time travel for its own sake, it's also a good one for fans of middle school girl friendship drama.
And now I will treat myself to a round of "What does Kirkus say?"
Total agreement! Kirkus says: Her transition to her new life is awkward but realistic, and the focus of this charming novel is always on friendship and loyalty. Rewarding and uplifting."
So there you go.