If you're using Marvin-3:
On main screen under "Collections and Lists" select "All your books".
Click on menu icon in upper right corner.
Under "Multi-Select" choose "Select multiple books".
You are now in multi-select mode as indicated by red circle/checkmark on top of screen.
Tap the books you want to delete. The counter near the red circle will increment up/down as appropriate.
When all selections have been made, tap red circle again.
Select "Actions" and proceed with CAUTION because the action will be applied to ALL the books you have selected. You can perform several actions: add to reading list, mark as read, rate books, delete, etc.
Multi-select is a very handy and powerful tool! Advisable to wear safety glasses and steel-toe shoes!
