Most of the books I read don't require the device being activated to read them. It's still a good idea to have it activated though.
For example if you want a book from
The Baen Free Library You would download the .zip file to your PC or Ax (If you have Total Commander for Pocket PC or another unzipping app on your device,)unzip the file, then put it on your storage card in a My Documents folder. Then either open Reader or tap on the file with file explorer.
HTH