If you use Bulk (single title) Mode metadata edit rather than edit in the bookshelf, you have a Next<> Previous button.
Full bulk mode, there is a tick box to get covers from book:
Steps
Search covers:false (get all books that have no cover set)
Select all (ctrl-A) de-select those you don't want to touch.
Tap 'E' Bulk metadata edit, tick the set covers box, OK
|