Do you want more detailed information on shrubs? I use this manual quite often to find information on plants I'm not familiar with.
It is written by Michael Dirr, an authority on plant material.

 

Do you want pictures? This book, also written by Michael Dirr, is similar but is illustrated.
I know landscapers who use it when showing clients plant material they would like to use in their landscape plans.

Search for more here: Books on Trees and Shrubs