It is so important once communication has been opened that the door is not closed.
The usual disclaimer: I cannot tell you what to do BUT if I were you I would not compare his reading of books to his gambling addiction. He has controlled his gambling and that will have taken a supreme effort as you know. Implying he has transferred his addiction could possibly trigger an unwelcome reaction. As someone who buries herself in a book, shuts the world off and can get irritable at interruptions but is not addicted, I would resent the implication that I am. I would not (and do not) have a problem when it is pointed out that my company is missed elsewhere.
It is difficult I know not to harp back to the gambling addiction and see it reproducing in a different medium but if it is not happening then, in my opinion, it is dangerous to raise the ghost at the feast.
Talk to him B but don’t forget to listen. Do it very soon and don’t let it fester. Remember you can always suggest he talks to others, such as his GA, about what is worrying you – reinforcement from outside the relationship is terrific.
I love the hollow lemon – so much better to make them that to have them thrown at you – not much good in a gin and tonic though!
Good to see you again