I took a book on my iPod touch on a canoe trip once, and found that the battery lasted for about five days, but I didn't read a lot.  It was very small, lightweight and made for some pleasant reading.  I might do it again some time.  I like reading books on the iPod, such as on a plane, or in the car.  It is very light to hold, and the night reading setting is easy on the eyes.

We always take a couple of small paperbacks, and exchange them when we are done.  Kent Krueger books are favorites, or something light--grisly murder mysteries are favorites.  Not something we would read at home and nothing serious.