https://www.librarything.com/mds

Melvil Decimal System (LibraryThing's equivalent of DDC, apparently in an attempt not to run afoul of the OCLC's Trademark.)

https://www.librarything.com/topic/85852

People circa 2010 interested in exporting their Library Thing book data to print out on library card catalog cards.

(I'm not the only one...)

https://www.librarything.com/profile/MEMBERNAME/stats/ddc

https://mleddy.blogspot.com/2005/05/tools-for-serious-readers.html

Interesting (now discontinued) reading list product from Levenger that in previous generations may have been covered by a commonplace book but was quickly replaced by digital social products (bookmark applications or things like Goodreads.com or LibraryThing.com).

Presently I keep a lot of this sort of data digitally myself using either/both: Calibre or Zotero.