Metropolitan Library System users can download books to their iPhones

The electronic books are automatically returned to the system at the end of the lending period. Electronic books will not have much of an effect on late fee revenues, which make up less than 1 percent of the library system's total revenues, said Kim Terry, director of marketing and communications for the Metropolitan Library System.

The library system has rights to a limited number of copies of each electronic title, which means library cardholders might have to wait for a book to become available before they can download a popular title.

For example, the library system might have only one copy available for download at a time of some book titles. Other more popular books might have several copies available for download at a time, said Kellie Delaney, manager of Web development and support for the library system.

The new iPhone application has been one of the most-requested services from library users, Delaney said.

“This is just one way we can help our customers and show them we're trying to maintain what they're wanting,” Delaney said.