A book on no shelf

This book does not exist. Its status does not either — the shelves know reading, want and read, and this one says abandoned.

It is here to prove what happens next. An unrecognised value groups under Unsorted rather than being silently dropped, which is the rule that makes changing a page's type safe: convert a Cinema page into a Library page and its films arrive as books on no shelf instead of vanishing from the tree.

Drag it onto a real shelf and the foreign value is cleared rather than overwritten — the difference matters, because a status nothing reads is worse than no status at all.