In discussing his favorite bookstores, Ryan David Jahn mentions that he only buys used books if the author is deceased. I take his point immediately, and I, too find the question of buying used books written by living, potentially royalty-earning authors to be a question that deserves some thought.
Of course, in some cases the damn books are out of print, so there's no ethical problem at all.
In other cases, I may stumble across a hardback copy of a book I prize, but own only in paperback. There again I'm not troubled; I shoveled out the cash once, and usually the hardback is out of print.
The tricky bit comes with books I don't own in any form, that are still readily for sale as new books. Do I, like Ryan, always hold out for a new, royalty-paying copy?
Well, sometimes I do and sometimes I don't. One of the joys to me of a used book shop is stumbling across something I might not have seen otherwise, and might not be altogether certain I really want to read. But, what the hell, if the cost is low...
The only way I can make up my mind about the ethics of this is to consider the "do unto others" aspect of the whole thing. Would I prefer that somebody buy my own books new? Sure.
On the other hand, if someone stumbles across a book of mine used and says, "Hmmm...looks interesting...maybe..." then do I have a problem with them buying it used? Not at all.
Do I mind if someone goes on Amazon intending to purchase my book new, and then sees all the used copies and decides to buy one of those instead?
Not really. I'd naturally prefer that they bought the book new. Hell, I'd prefer that they bought two new copies, one to read and another to be kept in mint conditions behind a glass-doored bookcase, but I'm glad that they're buying the book at all.
I don't object to libraries lending out my book. And I don't object to people passing a copy of my book on to friends.
Back when Thomas Harris' Red Dragon first appeared in paperback, I bought a copy, read it, passed it to a friend, who read it, and passed it on...if I recall, by the time it got back to me, something like 27 people read that poor, broken-backed, tattered copy. So Harris missed out on some royalties there. On the other hand, though, by the time Silence of the Lambs came out, we'd all finished graduate school, and I bet he sold 27 extra copies of that one.
I find this too be a gray area, not only ethically, but in terms of my own preferences. To put it simply, more money is good...but more readers is even better, and I'm not sure where the trade-off lies.
More money and more readers would be excellent, in whatever proportions.