[chaley]

Originally Posted by millan

-"found extra titles" (3501) out of (3505)
- "mark all for delete" then "delete marked"

or wait for another "set of steps" please

That "found extra titles" says that only 4 books in your library are "good" and that 3501 books are bad. I think that there is no point in trying to recover the library. You will be better off rebuilding it from the beginning. It would also be a very good idea to determine how your library was destroyed so it doesn't happen again.

What I would do:

1. In one copy of the library, merge the OPF and the book files:
   1. Find a "duplicate book" where one folder has the OPF file and the other folder has the book & cover
   2. Move the OPF file to the folder with the book and cover.
   3. Repeat for all 3500 books.
2. Create a new calibre library named whatever you want.
3. In that new library, select Add books / Add books from directories ... (One book per directory)
4. Point it at the copy where you moved the OPF files
5. Let it run

If you are willing to lose the book metadata than you can skip the merge OPF & book step.