Yes. If you are interesting in joining the program and want to take a look at current titles, you can view a list of them here: http://guides.masslibsystem.org/cec/home/content (see the "Title List" section). The list is updated quarterly.
Current participants can find an updated title list in OverDrive Marketplace. Login with your credentials then navigate to the "Insights" tab then "Title Activity Reports" to "Title status & usage" to run that report.
The size of the collection increases monthly. For the latest count, see: http://guides.masslibsystem.org/cec/home/dashboard.