To delete a notebook, you must first select one or more notebooks to delete. To select a notebook, long press on a notebook in the list. To select multiple notebooks, tap other notebooks after a single notebook has been selected. After selecting the desired notebook(s) to delete, choose Delete (trashcan icon) in the upper right corner of the screen or from the overflow menu.
To delete a notebook, long press on a notebook from the notebooks list, then choose Delete from the context menu.