Add this to the list of things you can do with your smartphone and other mobile devices: check out ebooks from your county’s public library. According to the National Association of Counties (NACo), more than 35 county-run public libraries are using mobile apps to make their services available to residents 24/7.

One example is Monmouth County, N.J.’s “Library on the Go.” The library’s website invites residents to “download ebooks and audiobooks anywhere, anytime.” The website guides users through the process, featuring colorful book symbols noting new ebooks or audiobooks, recently returned items and the most popular selections. There is an audiobook for “War Horse,” the subject of a recent Steven Spielberg film, and even ebook classics like “A Midsummer Night’s Dream.”

County residents with library cards can browse the library’s online materials, check them out with their library card and download them to their computer or mobile smartphone. And, there are no late fees; the titles automatically expire at the end of the lending period and are removed from the user’s device. Patrons can check out only five titles at a time.

A similar project launched Feb. 1 in the Cincinnati-Hamilton County, Ohio, library system. A mobile app allows patrons to check out ebooks and audiobooks, search the catalog and submit questions. Patrons can also use their smartphones to check out books by scanning them or to find out where a particular book is available.

The library is paying for the project — which cost about $9,000 for initial implementation and almost $15,000 in an annual subscription fee — through operating funds. The app was developed by the Silicon Valley-based tech company Boopsie. The company also developed mobile apps for libraries in Santa Clara, Los Angeles and Seattle counties. Other libraries are developing mobile apps in-house, “with more being added weekly,” according to NACo.