Sometimes it can be useful to mark all the books, ie a column tick or something.
Then restrict the sort to that.
Then you can sort again on size or format, date etc, to make selecting books (Shift+Click) easier but it really depends on the books
Make sure you know the short cut keys for advancing to the next entry in the duplicate plugin, as that can also speed things up if doing it that way.
Don't forget to try the fuzzy search and other options, as you probably have more duplicates than you think