Your shelf is empty
Tap the + button and photograph your first book.
The title page gives author & publisher; the copyright page gives year & edition — the details that decide value.
Your books currently live only on this device. Turn on cloud backup so a lost or wiped phone can't erase your collection — and so you can open your shelf on another device.
A one-off backup file on this device (includes all photos). Good for keeping a copy on your computer.
Shelfward keeps your catalog on your device. Nothing is shared unless you choose to.