[1] The central premise of the stories is an Earth that has discovered access to alternate universes where history proceeded differently.

In all of the series the "home timeline" was running low on resources, and it has used its knowledge of time to covertly import supplies from other Earths and save their civilization from collapse.

The books are young adult novels with teenage protagonists, who frequently become stranded in dangerous alternate worlds and must adapt to survive.

In two books it ends with successful consummation, the protagonist from an Alternate timeline getting exceptional permission to come to the Home Timeline; in one book, lovers must say goodbye with a tearful heartbreak; and circumstances in one make it end with boy and girl becoming staunch foes, despite their mutual attraction.

This shows considerable restraint of the author Turtledove, who is famous for writing scenes of unfettered sexuality, violence and profanity in his adult novels such as the series of Worldwar, Southern Victory, and The War That Came Early.