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LibraryThing is an online service to help people catalog their books easily. You can access your catalog from anywhere—even on your mobile phone. Because everyone catalogs together, LibraryThing also connects people with the same books, comes up with suggestions for what to read next, and so forth.
In April 2013, LibraryThing staff and members collaborated to write What makes LibraryThing LibraryThing?, a blog post outlining what we see as the key elements of LibraryThing.