I am using Kobo Touch. In one of the devices, device information reads
Software version: 2.0.0 (r41166, 7/12/12)
The other device shows:
Software version: 2.0.0 (r41166, 12/07/12).
I tryed two methods to perform the deletion: (1) I pressed the written lines icon on the Library/Books list of books; this opens a menu with the options:
Mark as Finished
I choose the option "Delete". The other method is to delete the book directly, using the operational system of my computer.