Actually you don't need ADE once you have authorized the device. I actually uninstalled Adobe from one of my computers once the authorization was done. Reader Library is all you need, ven for library books.
Still ADE should recognize your device. I'm not anywhere near my reader right now so I can't check how it behaves, but before you get too desperate, try using just Reader Library!
Edit: I didn't notice you were on a Mac. Im not, but it should be basically the same, one would think.