If you use the
Logos software or mobile app, you can get two free books each month. I knew about
the one on the Logos site, but I didn't realize until just now that Logos has a Catholic version of the software called
Verbum with its own
free book. As far as I can tell, the libraries are interchangeable, so any resources you have show up in either version of the software, apps, and
Biblia.com.