Under the first sale doctrine, he has a right to do whatever he wants to the bytes that he has purchased. The underlying content (i.e., the "book"), however, remains subject to stuff like copyright, etc.
But in all seriousness, the DMCA does authorize DRM-cracking if necessary to allow the customer to enjoy the full private use of media they have purchased
But in all seriousness, the DMCA does authorize DRM-cracking if necessary to allow the customer to enjoy the full private use of media they have purchased