If you borrow books from your local library, you may already use Libby to read them on your phone, Kindle, or other digital device. You may also already know that Libby lets you enter and easily switch among multiple library cards, and that several libraries have reciprocal agreements with other libraries, so a card from one could unlock access to another. ReciproCard, a “community-driven discovery tool,” makes finding those reciprocal agreements easier. Type in the library where you already have a card and see a list of other libraries that offer access, either directly or by applying for a new card online or in person based on residency.

(There are also a handful of libraries that provide cards to anyone for a small fee. For example, Broward County Library in Fort Lauderdale offers access to its 2.8M-item digital collection for $38 a year.)

Thanks to ReciproCard, I learned that as a cardholder at San Mateo Public Library, I also have access to the digital collections of MARINet (2.8M items) and NorthNet Library System (207K items). I was also reminded that as a resident of California, I can get a card from any library in the state with proof of state residency and a visit to the local branch.

There are some inaccuracies, being a community-driven tool. For example, it shows San Francisco Public Library has a reciprocal agreement with Santa Clara County Library, but SCCL requires a valid local address when you apply online. (SCCL does not appear to require confirmation of that address. Neither did the Queens Public Library when I tried an old Brooklyn address—purely for testing purposes, naturally. Both cards will likely expire without a visit to a branch, however.)

I now have six library cards in Libby and plans to acquire a few more. Just in time for summer reading season.