Re-reading a book is a lot like re-watching a film for me, I don't want to do it immediately, but there is value in doing it some years later where the details become less certain. I'm actively aware that even during tasks such as talking, my brain condenses and throws away most information. The import thing really is to develop and capture the right abstractions.
There are a few books I have gone back and read simply for enjoyment, for example Hitch Hiker's Guide to the galaxy was a pleasure to read. Some more dense materials that I know I will gain a lot from, I find it difficult to muster the motivation to re-read.