Librarians Rejoice: Android App Helps Tidy Bookshelves.

"The books have to be tagged first with a machine-readable label, but once that's done the user can walk down the shelves looking for red crosses in a sea of green ticks, which change to a green tick showing which direction the problem book should be moved in to put the collection back in order."

"Attaching all those labels is the obvious problem. The app can't read the often poorly-attached numbers - Dewey Decimal references - that adorn the spines of library books. Instead it requires an entirely new tagging system that can be read with a phone's camera and processed by an Android application."