AFter I linked my LibraryThing listings to Paperbackswap, I noticed that many books at PBS have large numbers of copies available, and large numbers of copies wished for.  How does that happen?  If it were just a few, I could understand problems with format, condition, etc.  But one of the titles had 417 available and 103 wanted! 

The only thing I can think of is they are different ISBN numbers, format or something....

When I was playing around with Librarything when I started with it a few years ago, I found the numbers listed for PBS books way off. Not even close.  I don't know where they get their numbers, how often, or when. 

Nice Site, and I use it a lot, but I just don't trust what they say about other sites.

can you give a sample ISBN so we can check?

I can see that happening pretty easily, lots of mass market paperback available, lots of hard cover, audio, and trade size wish listed.

The problem with Library Thing is they consolidate all the different versions when they calculate what's available vs. what's wanted. Just as an example, I picked a book off my shelf "Turning Angel" by Greg Iles.

The library thing page is here: http://www.librarything.com/work/174183 (you might have to be logged in to see it).

If you click on Get This Book in the right column of the LibraryThing page, you go to a page where it shows all the different places you can swap for or buy the book. If you scroll to the bottom of the page, it says PaperBackSwap 570 available/1 wanted. When you click on that link, it shows eight versions of this book, seven of which are available and one that is on a wish list. The one that's on a wish list does show 0 available. The problem is the display on the previous page is misleading because they've added up all the paperback, hardcover and audio versions as if they were interchangeable.

If you go to the PBS Book Browser and search for the title "Turning Angel", you get twenty different ISBNs, several of which have wish lists. So not only does LibraryThing display the totals in a way that doesn't make sense, it's not even including all the data. I would not rely on anything you see over there.