How do I put this version of my book on Amazon?

I have a paperback version of my book (self-published) on amazon.com. The vanity press handles this. However, the same vanity press ran a few hundred copies of this same book (with a few revisions) in hardback. The problem is that the hardback has a different ISBN number. I contacted amazon.com a few years ago and inquired about this, and they said I could not put the hardback on their website because it has the different ISBN number. I think the hardback might sell a few copies. No one buys the paperback, and the one review is poorly written (albeit appreciated). The main problem with the book (published in 2002) is that it is too intellectual for most readers, but I'm sure there is a niche market out there. Do you have any ideas on how to do this? The vanity press went bankrupt, though I maintain contact with the person who built the small company.

Hi David,

It is normal practice to have different ISBNs for paperback and hardback books. If it is a niche book, I would suggest uploading it to Kindle.