Re-reading is one of life's great pleasures. At present I'm revisiting Margot Livesey's wonderful book about writing (and reading) The Hidden Machinery. What a pleasure it is to read such intelligent insights! What deftness of touch! And how beautifully she conveys really important information, with a lightness that is utterly beguiling. If only I'd read this book about two decades ago (alright, it wasn't in existence two decades ago, but I think you know what I mean) I could have been a much better writer and a far more appreciative reader, too.
If you're interested at all in writing and reading, rather than in simply decoding words to follow a plot, this is a gem to be treasured.