Swap shop marketplace

I am looking for a module or a way that I can run a swapping platform.

I want to add some additional functionality to my book blog where people can swap their books.

Can anyone advise me how I could go about doing this.

I method could be to create a content type of book which gives details of the book, I can then just add vocabularies and categorise the books.

But where it gets tricking is how I can get people to notify each other that they want to swap, save / watch swaps, and notify each other once someone wants to swap for somethign they have.

Any help appreciated.