Lots of people do it-I know that just sitting there can be kind of awkward. I find it easier to read maps or short things, otherwise you could miss out on someone (like a CM) who might like to talk to you. If they come by and you're engrossed in a book, they may be hesitant to speak to you and disturb you-I've noticed this with servers. What I do that seems to work, for me at least, is I bring a little 69 cent spiral notebook and jot notes during my meal-where I've been, what I've done, what I've eaten, etc. When I get home, I tuck it away with my other mementos and later I find it fun to go back and read. It's also useful for answering questions on these boards-sometimes you forget certain details about your trip you want to share.