Originally Posted by HarryT
But you're not "letting a friend borrow it"; you're giving your friend a copy of the book. Previously only you had a copy; now, both you AND your friend have a copy. Two books exist where previously there was only one. It's like photocopying a paper book and giving your friend the photocopy. That's why this is not permitted.
No, I'm giving him my licence to read it for the loan period. The actual file of 1's and 0's is immaterial, what matters is the DRM and who can read the book using it.