Rather than relying on one book that is read each day of the week (as our traditional units do), these units revolve around one theme and are dependent on a variety of books to enhance learning.  They allow a more in-depth study of one particular topic-- giving you the freedom to capitalize on your child's current interest.  Simply choose a topic, get the core books you need from the library, then print out the lessons and begin a fun, memorable, extended learning time with your child(ren).