If you look at the locations of a book, you may see the location as "Unavailable, CRC - Digital Lending" as illustrated in the picture below.
These books are marked as "unavailable" because in order to offer a book digitally, the library must remove the physical book from circulation. The "unavailable" for books in the CRC - Digital Lending location only refers to the physical copy of the book. These books are available digitally.
To access a digital book, scroll upward from the Locations section of the page to the View Online section and click on one of the digital book viewers, as illustrated in the picture below.