It's the feeling of escape.
You curl up tightly in an overstuffed chair. Pull the blanket in close. Get lost in another world. It is the beauty of reading. Mysteries were always my favorite. I would spend hours reading about how Encyclopedia Brown out-smarted the bully or how Trixie Belden once again lived through a death harrowing experience.
Since I'm homeschooled, my schedule is so very flexible. But, early on, I took advantage of that. I would slip a Nancy Drew novel under a blanket while pretending to read history or "study" science. Whenever Mom would walk by, I would slyly slide it back under the covers and pretend to care about James Garfield.
I would get reprimanded. Then, I'd do it again, and again. Obviously, I didn't learn. And, I don't think I ever will. A good book is always more enjoyable than anything else. It envelops you.