19. The system of claim 15 , wherein the mobile device is further configured to prompt a user who captured said one or more photographic images of the bookshelf to mark the returned one of the book identities or the returned further book identity as being correct or incorrect.
20. The system of claim 19 , wherein the mobile device is further configured, when the user marks the returned one of the book identities or the returned further book identity as being incorrect, to prompt the user to provide a user-supplied book identity corresponding to the at least one of the regions, and, upon receipt of the user-supplied book identity, the system is configured to update a training set to reflect association between the user-supplied book identity and the one or more visual features.