Hey gmixstudios,
If you really want to add to your rhythm playing, and learn some very useful patterns. Check out these tutorials, and you'll learn methods that can be used in many styles.

http://www.guitartricks.com/tutorial.php?input=832
http://www.guitartricks.com/tutorial.php?input=846
http://www.guitartricks.com/tutorial.php?input=869
http://www.guitartricks.com/tutorial.php?input=910
http://www.guitartricks.com/tutorial.php?input=917
http://www.guitartricks.com/tutorial.php?input=965

After these, go for this one for some totally different strumming ideas.
http://www.guitartricks.com/tutorial.php?input=995

I know your post was about a book, and I don't know of one. These tutorials will definitely give you new ideas for rhythm, and maybe new ways to use what you already know.