I missed a lot of sleep for my books at that age. It did have some of the negative qualities of an addiction, and
still can drag me in -- I broke my toe last week, and tried reading a novel to keep my mind off the pain, and finished it around 5am. And realized I was exhausted, and my shattered toe was throbbing madly, and I hadn't even taken any pills for pain.
These days I mostly read serial online fiction, because it comes comes in metered doses; e.g. http://pactwebserial.wordpress.com/
My parents quickly realized that "go to your room" was totally a non-punishment for me, and they couldn't reasonably do anything to stop me from reading after they'd gone to bed.
I'd suggest working with your son on flexible solutions -- it could work to ask him to always read more advanced stuff (with more challenging vocabulary, plot, etc.) at bedtime so that it takes more brain-work... that makes it a bit more likely that he'll put it down when he's really tired.
The main thing (I think -- my oldest is only 5) is to see if he himself thinks there's a problem, and (if so) help him hack his own lifestyle, acknowledging that you don't know the answer, but you can help experiment & track the results.