Multi-document site using RTFM

I would like to create a multi-document site using RTFM. Each document would be its own self contained hierarchy of pages. The main home page would have links to the individual documents.

One way to do this, I suppose, would be to make a separate GRAV site in each subfolder (/book1, /book2). That is the effect I am trying to achieve, but hopefully there is a cleaner way to do it.

Any suggestions would be greatly appreciated!