図書館イズム is a library management app designed for avid library users. Users can register their favorite books and frequently visited libraries, categorize them with statuses (want to read, reserved, borrowed, read), set reminders for due dates, add custom tags, leave feedback notes, and directly check the availability and lending status of books in libraries nationwide. The app allows for book registration through database search, manual input, or barcode scanning. Users can also register preferred libraries, manage book statuses, sync data across iOS devices sharing the same Apple ID, and export/import book data in CSV format for easy backup and sharing.