As most Amazon.com shoppers know by now, you can buy used books direct from other, ordinary folks out there through Amazon.com's Marketplace. Similarly, you can opt to sell your used books through Amazon.com, with Amazon taking a small commission off the top.
Buying used computer books makes perfect sense to me. These types of books are typically more expensive - $40-$60 a pop new - and have little value once the owner moves on to a new technology. Not surprisingly, you can save a large amount of money buying such books used, especially if the technology's outdated by a few years.
The reason I am blabbing on about this is because I have always wondered what percentage of Amazon shoppers buy new vs. buy used. Well, now I have an idea as to this figure. See, Amazon offers an Associates Account, where you can link to a book from a Web site and make a percentage of the sales price if a shopper clicks through your link to buy the book. (The books on the right-hand side of this page, for example, will direct you to Amazon.com passing in my referral ID.) A while ago, Amazon started giving comissions for people who bought used books as well. So, I can look at my Amazon Associates report and see how many people bought used vs. bought new.... and the numbers? 16.9% of people who bought a book clicking through a referral link of mine, bought used. 83.1% bought new.
These numbers, of course, only reflect the new vs. used purchases for computer books focused on Web development, so they might not be indicative of the entire set of books sold by Amazon. What surprised me, though, was that the purchase of used books was as low as it was. I assumed that more people would be buying computer books used than new, as virtually all of the books I buy from Amazon these days are used.
In closing, I'd like to address buying used vs. buying new from the prospective of an author. Ideally, all consumers would buy new copies of the book, as I don't see a cent in royalties for those who buy used. However, as I've stated before, you don't write books to become rich. Most computer trade books written in the Web development field don't surpass the advance amount, so it's kind of a moot point. Also, in some cases the price may be the deciding factor on whether or not a reader buys your book. They might pass on the cost of a new copy, but read it if they can get it used. I'd rather have my book read and not receive my royalty share, than not have it read at all.