wnload problems

I have been downloading books on my Nook reader for a couple years now, always successfully.  However there is one particular book that will never download properly.  I put it on hold, download it when it becomes available.  But when I try to transfer it to my reader I always get a message " book has been returned."  I put it on hold a 2nd time but when it became available, same problem.  Whats up?