One that comes to mind is Tolkien, the Lord of the Rings trilogy. I read this when it fist came out and was so absorbed that I'm sure I read every sentence. I lived for a while in Tolkien's alternative world and on some days had a hard time returning to reality.
Coming back to it long afterwards, I .... well, I did just what Gopnik describes. The moral psychology remained pwerful and relevant. But I found myself more interested in minor and even tangential characters than in the heroes and villains. And I did a lot of skipping -- including most of Frodo's final journey to Mount Doom. The return to normality -- with that lovely, comforting last sentence, "Well, I'm back" -- was just as satisfying (if implausible) as before.
As anyone else had similar experiences when revisiting one of your serious favorites from long ago? And how did you handle it? OR did you love the book as much or better than before?