I reread every novel I read many times and every time I notice different things.
First read tells me the story, second read I begin to understand the nuances and subtleties of the story, third time I start to appreciate the language, fourth time I notice subtleties in the plot I had missed before. After that, for books I really love: Jane Austen, I just enjoy rereading the book for the sheer pleasure of enjoying it yet again - and I keep discovering, things in it that have never struck me before.
I am currently doing a class studying 'Middlemarch' by George Eliot. I studied it at A level and have reread it a couple of times since (nearly 50 years), but reading it with a tutor who has us looking at the language used, how it varies, how the authors voice changes and so one is adding this book to one of those I am now going to be coming back to again, again and again, just to admire the craft of a superb writer.