title_body: Delete all directly import/sent kindle books
upvoted_answer: It might be easier to go to the Manage Content page, select Your Devices tab, put a check in the box for the device you want, then in the popup look for the option, View Device Content. 
  
  Doing that should let you do a mass deletion of items on a device without having to worry about deleting it on the cloud. By the way, for my account, it looks like View Device Content has two listings for each device: one for audio recordings, another for ebooks. You will see the View Device Content option only in one of those two listings. This should do it.