Paper for sure. For a novel, I just find an E-reader too impersonal. A paper book is much more cosy.
Also, if the book's ending sucks, I can throw it across the room. I did that when I read Crichton's Sphere.
I also can't do audiobooks. My attention just drifts too much and I miss important things. I do listen to radio dramatizations though. The BBC does lots of them and many are on the Internet Archive.