When my wife and I do our annual 3 week trip we generally take 3 or 4 books between us.  I fish, my wife doesn't so she reads 3 books to my one.  Still, 3 or 4 books can add up weight and bulk-wise so I looked into an e-reader as a possible solution.  The problem for us is that a fully charged e-reader might make it for 5 or 6 days before it needs re-charging.  It's not like you can carry extra batteries so that more or less put the kibosh on e-readers for us.  If it weren't for the charging problem, it would be a great solution.  For shorter trips it might make sense except for shorter trips you'd probably only take one book, so what's the gain?