Re-reads ... I love to re-read! There are some books I've re-read so many times, and it seems each time I understand something more, or am more 'in' the story. It's almost like the life experiences I've had since last reading it might have changed my stance a bit (metanoia) and so I read it from a different vantage point.
If it is a series of books, say, for example, the Harry Potter books, and I read Harry Potter and the Philosophers Stone after not reading it in a while, I'm awed again by the sheer richness of the world which JK Rowling created -- and see, even in some of this early (and relatively light-hearted) book, foreshadowings of the entire series! This can happen with all of the books which are of series. This can also happen with a favorite book - one of which, currently, is Ready Player One.
I have found that I tend to acquire books which I have read more than once. I have been fortunate to have some fantastic libraries from which to check out books, and thus find out if I like a book, but if I check it out a couple or three times, that's an indication that I'll end up somehow, acquiring the book (or the series of books). That's what happened with the Dresden Files, the Mortal Instruments, (Twilight), In Death, Tortall, Paladin Prophecy, The Raven Boys, Wheel of Time, House of Night, Harmony, Camelot, Sandman, LoTR, Darkover, Nero Wolfe, and yes, Harry Potter books (along with many others). I also collect books by author - Agatha Christie, Dick Francis, Dan Brown, Michael Crichton ... oh so many ... and reread them. Some folks just 'feel good' and their goodness comes through in their writing and it's lovely to immerse oneself in their presence while reading their stories.
"You have the inborn natural right to remain silent. Don't think about it, don't talk about it, shuush ....... STILL." ~ Xaris