"In a neighborhood as old as this you might get a book back five years late, 10 years late, when someone moves or they're cleaning out a house," Librarian Darice McKay.
Webb was 83-years-old when she checked out the collection of short stories and records showed she died a week before it was due to be returned.
"It's hard to come back as a ghost and return your late library book," Wells said.
The book remained in a trunk full of Webb's belongings for 80 years until Johnson discovered it and decided to keep it to himself.
"I really enjoyed reading it, it's one of the reasons I held on to it," he said.
The library estimated that the book would have accumulated $3,650 in late fees at the modern rate of 10 cents a day, according to the San Francisco Chronicle.
Under the library's current amnesty program, which has recovered 2,000 overdue books since Jan. 3, Wells and Johnson were permitted to return the book free of charge.
"In a neighborhood as old as this you might get a book back five years late, 10 years late, when someone moves or they're cleaning out a house," librarian Darice McKay said.
The library must now decide whether to place the book back into circulation or put it on display.
"This is something I know people will want to read," librarian Luis Herrera said.