I had several books on my BS that I put on hold as they are NOT available.  But for some reason, somehow, the books ended up on my BS twice even though only listed once.  They were all posted today.  I discovered the error when someone requested two of the books, which I then had to decline because they are not avialable. I've rechecked my BS and found 2 more duplicates that I've removed.  Doesn't the system prevent two listing of any book on the same BS?  And I have no idea why it put 2 books up when I listed it once!  GRRRRRRRR!  Anybody else have duplication problems with their BS?

I will have to go check, but yes your assumption that same book (has to have same ISBN) cannot show up twice on your shelf.--so it must be glitch!