Bill Bryson has written a wonderful short essay in The New York Times on why he always has reading material on hand with him. He says it started with an assignment from Granta to write about the aurora borealis.
There is little to do in Hammerfest in winter but go for creeping
walks in the pitch-blackness, watch the single channel of Norwegian
television or read. I read. By the end of the second week, I
had read everything in my possession, including the labels inside my
suitcase and every word of the three English-language magazines sold in
the local newspaper shop. I reached the point where I was calling in
twice a day to find out if the new issue of Woman’s Weekly had arrived. Since then I have never ventured abroad without packing more
books than is strictly sensible and enough magazines that I can always
have one rolled up in a back pocket. More often than not, it is a copy
of The Economist, which I like very much except sometimes when it
reviews my books.
Hemingway was known for keeping at least a book in his back pocket. I nearly always have reading material with me as well. Once, I found myself stranded for three hours in a shop in Shenzhen while my wife and my sister-in-law systematically went through all its wares. Luckily, I went prepared, and my wife was praised for her "patient husband…"