The Sisters in Time series does not have a new book coming out soon. The latest book, Laura's Victory: End of the Second World War (Book 24), was published in April 2006.
The first book in the Sisters in Time series, Sarah's New World: The Mayflower Adventure, was published in February 2004.
The Sisters in Time series primarily falls into the Christian Historical genre. This middle grade series was written for ages 8-12, but can be enjoyed by older readers as well.