Loads of real books, many from charity shops, and a lot on the Kindle. I never used to think I'd take to a Kindle, but have found it very useful when
a) going away with a friend, hand baggage only, so no room for the 4 + books I'd normally take to last me a week,
b), being able to read in bed without disturbing dh. Esp. in hotel rooms. At home at least I can sleep in another room if I want the bedside light on.
c) being able to make the font size a bit bigger - I've been known to pass on books I'd otherwise like to read because of a very small font,
d). Kindle means I've read some seriously fat, heavy books I'd otherwise not bother with, since too heavy/awkward to read in bed.