I have duplicates of a few titles. And I have just about everything, except Changeover and Islands of Chaldea (coming soon!). I even have a copy of Yes, Dear, a picture book about a little girl who finds a magic leaf, but I'm not sure where it is right now. I thought I knew, but it wasn't there.
Some of my copies are really ancient and I would like to get new ones before they fall completely apart. Check out my copy of The Ogre Downstairs: hideous cover from 1977, former library copy, and a paperback. The Spellcoats isn't doing much better; I picked it up used and it's from 1979. Though I actually quite like the cover! And Archer's Goon, also bought used--in the 1980s--and starting to disintegrate.
As you can see there is not much in the way of matching sets. I absolutely loved the Dalemark covers that came out some years ago, but I only have Drowned Ammett; I wish I had the others too. DWJ mostly suffered from horrible cover art, but those Dalemark covers were lovely, and quite a bit of the newer stuff is great. I don't have any of those nice UK covers you see now, but they are pretty good.
So there you have it--my DWJ shelf.