There's something deeply upsetting about the notion of someone – and one day, yourself – reaching the point where you put down Pride and Prejudice and think, well, that's the last time I'll read that. When I read a book I really love, part of the pleasure for me is the knowledge that it's not gone forever; that I'll come back to it in a couple of years' time. Recognising that a point will come where this isn't the case could well constitute the closest I've ever come to acknowledging my own mortality … Then, there's the question of which books you'd store up for a final read. I'd put Wuthering Heights in there, I think, and definitely Updike's Rabbit tetralogy, and Bruce Chatwin's On the Black Hill. If it's not too maudlin, I'd be interested to hear what you'd choose, too. Either way, I recommend Athill's Yesterday Morning heartily – whether you've read it before or not.A bit morbid this, but Sarah Crown's post on The Guardian blog certainly struck a chord with me, as I know I'm (subconciously) working on my mental list of books I want to revisit "before it's too late".
Old friends like Coetzee's Waiting for the Barbarians, Carson McCuller's The Heart is a Lonely Hunter, D.H. Lawrence's The Rainbow will definitely have to be saved up for the long goodbye.
I remember an elderly British novelist telling me some time back about how he was giving away most of his most of his personal library - books he'll never read again - and just keeping the few that he would want with him. I'm sad I didn't ask him what those most precious books were.