I buy used paperbacks (nice and lightweight) from the library sale tables. I can leave them, give them away, trade with fellow travelers--and if I happen to arrive back home with them--or with new acquisitions--I cheerfully donate them back to the library (getting a donation slip for my taxes). Garage sales are another source. And a month or so ago, I bought several new hardback books at Target for $.25 each. I'm currently reading a very interesting book titled Poison. (which, now that I think of it, might be a good book to be reading on a SW flight when I want to discourage anyone from taking the empty seat next to me)