How to delete a notebook in Evernote for Android?
To delete a notebook, you'll need to log in to the webapp. Your notebooks will appear on the left side of the screen. moving your cursor over (or tapping, on your device) the notebook you wish to delete will show a triangle to click for a drop-list from which you can delete the notebook.

Edit: According to this link, you can't do it from the Android app yet. http://discussion.evernote.com/topic/29175-helpdelete-notebook-on-android/