Imagine being 11 years old and transported from your suburban American life to 1980s East Germany. That's Noah's life in Cloud and Wallfish by Anne Nesbit.
Josie and Alec are the best of friends, even chatting daily late into the night. Except Josie lives in 1915 and Alec lives in 2015. The Boy from Tomorrow by Camille DeAngelis is a cute children's story of best friends, even across time.