Is there a setting when scanning books to add to not add duplicates?

I started using LibraryThing, but then moved and my books are now in a different order and it's impossible to see where I left off. Is there a setting so that while I'm scanning it just skips adding duplicates? Or, conversely, is there an easy way to purge duplicates after the scanning session?

>1 JenniferinFL: You can just click on the red X next to the added book in the list that shows on the right hand side in "Add books".

>1 JenniferinFL: I believe there is a setting if you are uploading books by CVS file, but not if you are scanning manually.

I haven't scanned before, so I apologise if my answer isn't helpful. If scanning puts those books into your 'recently added' menu on the 'add books' page, that page should tell you if you've added a duplicate. A duplicate book with a different ISBN will have a message in green text which reads something along the lines of 'you have another copy of this work,' while a duplicate with the same ISBN will have a message in red that reads something like 'duplicate ISBN in your library.'

So keeping out duplicates is simply a matter of watching the 'recently added' menu and deleting books when they show up with a duplicate warning.

One thing to watch out for is digitised copies of a paper book with an ISBN; some publishers in the early days of ebooks didn't assign new ISBNs to their newly released ebook. What I usually do there is edit the existing record to be the ebook, move the paper book to the charity shop stack, and delete the newly added record. I've seen it in book bundles from Humble Bundle; what you get is a digitised copy of an old paper edition, so checking ISBNs on the copyright page only shows the paper ISBN. (The irritating thing now is for copyright pages to have all the ISBNs for paper and ebook editions; when I extract the ISBN in Calibre, it picks up the first one not the correct one-so I get books tagged as ebook with a paper media type.)

Even now it's common for 'clicks and mortar' RPG books (where you purchase a physical book and get a searchable PDF included) to not have a new ISBN. Here I just live with the 2 entries - 1 paper, 1 digital.

From what I understand from previous RSIs, it would put too much load on the servers to search your catalogue for existing copies of the same work, even when limited to an ISBN search.