You can select multiple books and remove them from your eReader. 

1. Go to your Home screen.
2. Tap the  My Books icon at the bottom of the screen.
   
   
   
3. Tap the  Menu icon.
   
   
4. Tap Manage books. The Manage Books menu will appear.
5. Tap the checkbox beside the books you want to remove.
6. Tap Remove at the bottom of the screen.
7. Select one of these options:

• Remove download: Remove the book from your eReader, but have the ability to re-download the item from the Kobo Cloud later. You'll still see the cover of the book on your eReader. This option is automatically selected.
• Remove from My Books: Delete the book from your Kobo account and all of your devices. You'll no longer see the book cover on your eReader or Kobo apps. To put the book back onto you eReader or Kobo app, you'll need to go to Kobo.com to restore the book from your Archive.

8. Tap Remove.