I'm really glad this thread existed when I went looking for help with ADE format library books. So thanks to the OP and to the other members who posted to the thread. The Bluefire Reader app works great on my iPad. I followed the website instructions to get the app authorized with my Adobe ID, and get the book file onto my iPad.
The only thing that confused me, and my reason for posting this in case it helps anyone else: I had to be connected to internet in order to OPEN a protected library book initially in Bluefire Reader. But it didn't say that, it just said the book was "unavailable right now, please try later." When I thought to turn the WiFi back on, and then selected the book again, it finally spun a little gear logo while announcing that it was verifying the library loan. Yay, then the library book opened, and now I can read it on the iPad while offline.
I am truly thrilled. I do not like just using the Adobe Digital Editions software to read protected library books on my MBP, and yet I am not one for trying to circumvent the DRM on the thing. I may not like the inconvenience of DRM, but I agreed to the terms when I got the library card and the Adobe setup, so that's life. This solution lets me abide by the terms and still read the books on my iPad. Thanks to all for the posts that caused me to give Bluefire Reader a try.