I have been trying to articulate for myself the precise pleasure of reading an excellent book.
It is a full-body pleasure. If I have reservations about a book, I feel it physically as I read. Some part of me does not relax, some part of me will not let go. With excellence and expertise, I am putty in the author’s hands. This has to do with trust. And hope.
It’s like having a crush on someone, too. There is a tingle, a physical excitement. I am my own best self in its company.
When I stop reading, there is withdrawal, hangover, need.
And when I have finished the book, it takes up its place in my mental geography. It is on my map of the house, and I can see it in its snug spot on the shelf, pulsing, waiting for me to be reclaimed by its pleasures again. I don’t always remember why, but I know it to be true.
Nathalie Foy 
Oh yes. ..and why is that some books stay with me forever and some don’t…like Lucky Jim..I think I felt so embarrassed for him .. he’s lived with me for years!
I get withdrawal too! Actual withdrawal; if I don’t do any leisure reading for a few days, I get massive unbearable headaches until I start reading again.