Groups would be good for spaces like an office. Users join the group and their collective library is visualized. Seeing who has what books, where the overlap is, and know who they might borrow it from.
Groups could also be used by friend groups, or to create an asynchronous book club.
In 1.0, users can only connect to other users. Books exist as global references, and “who owns what” is visible to each user. Only borrow and lend functions are available.
In 2.0 users can have person-person connections and can join groups. Groups are always invite only, and must be created by a user. Under each book, the user has access to group discussions. If a user is in multiple groups, they’ll see options to switch between group threads. (If a user leaves a group they created, they must elect a new admin.)
Can discussion happen off the app? Do you create a thread under each book? If you exclude any meaningful commenting features, would people text instead?