Seven Stories Up, by Laurel Snyder (Random House, January 2014), is a lovely introduction to the fun (and tension) of time travel for older elementary school kids (the confidently reading third graders through the fifth graders).
Annie doesn't know her grandmother. There's one picture of them together when she was a baby, and that's it. Now her grandmother is dying, and her mother takes her to the old family hotel in Baltimore to say goodbye. And Annie's one encounter with her dying grandma is enough to make her realize why her mother never wanted to go home.
But that night, sleeping in the old hotel, Annie travels back to 1937. There she meets Molly, a girl her own age, trapped by illness in her rooms and desperate for human warmth. The two become friends. Annie leads Molly away from the hotel to explore the city, and Molly teaches Annie how to use a dumbwaiter to good effect. Their friendship, especially Annie's encouraging conviction that Molly is well enough to have fun, ends up working something of a miracle....
The shenanigans of the girls are relatively mild. There's enough tension (from both the uncertinty of how Annie will get home, and the adventures of the two girls) to make the book absorbing, but not so much as to make things uncomfy. And the friendship between the two girls, both very engaging characters, makes for very pleasant reading. I wanted to join them in their adventures (except the roller skating fiasco).
Plus--bonus kitten! And also plus (though not so much as a kitten)--interesting look at depression era Baltimore. And as a further plus--it encourages empathy and an understanding of how cranky old grownups might have gotten to be the way they are!
I short, I enjoyed it lots, and I can whole-heartedly recommend it to my eight-year old self.
If you have a young fan of Annie Burrow's The Magic Half, give her this one. Or if this your young reader's first foray into time travel, have that one on hand, and then offer Charlotte Sometimes, by Penelope Farmer.