There are literally tens of thousands of used book dealers out there, and they're easy to reach.
Most list books on specialized websites such as ABE (I think ABE stands for Antiquarian Book Exchange)
http://www.abebooks.com which is the biggest such site. Another good site is Powell's [url]ww.powells.com[/url] which is a huge used book store in Portland, Oregon.
You can reach even more booksellers by going to megasites which search ABE and many other book sites. These are
http://www.addall.com and
http://www.bookfinder.com
Each has it's pros and cons. Try both to decide which you prefer.
By the way, when you look for used books on Amazon, Barnes & Noble and other similar sites, the books are not owned by the site. They are owned by small private dealers who are just listing them there. Websites such as ABE and the megasites below allow you to go direct to the seller.
I use the megasites when buying books for personal use (I've been in the book business for 28 years). It's worked well for me. There have been a few minor disappointments, but I've not been burned.
After finding some books that meet my price/condition criteria I look within that group for booksellers who list their phone number. Then I call to place an order. That way I know the book really is in stock (website listings can get out-of-date).
I start by asking a minor question about the book. In less than 30 seconds I have a pretty good idea of what the person at the other end is like. If I'm uncomfortable, it's easy to back out.
This reduces the risk of internet auctions where you're not always sure of what you're getting or who you're dealing with. Also, it cuts out time wasted bidding at auctions and not getting what you want.
Re internet auctions: 99% of the people are honest, but sadly a lot of them don't know much about the goods they're selling, and have difficulty accurately describing condition, edition, etc. A fast conversation is more efficient and more effective than a barrage of emails going back and forth.
Where there’s smoke, there may be salmon.