There are lots of places online where you can find rare and secondhand books — but one place you should check out if you’re looking for a Harry Harrison book is Fantastic Literature Ltd.
What’s so special about them? They are currently listing hardcovers and paperbacks of many of Harry’s titles, all in fine or very good condition – i.e. never been read – and these books were obtained directly from Mr. Harrison himself. And some of the more interesting items have been signed by the author.
And if you have all of Harry’s books, they also have stuff from a bunch of other authors… 🙂
Simon and Laraine at Fantastic Literature provide great service – highly recommended.