Try this:

IF USED('book')
  USE IN book
ENDIF
USE book EXCL
ZAP
USE book SHARED

>if anyone can advise what is wrong with the code below... i am trying to empty a table and can't get the exclusive use set to off again once it is packed...
>SELECT book
>if reccount()>0
> USE book excl
> DELETE ALL
> PACK
> SET EXCLUSIVE OFF
>endi
>
>many thanx!