There isnt much documentation and there is no recent documentation.
This project while in use in several production environments (mine included) isn't really maintained any more.
There also has been a maturity in the concept of CQRS and 'CQRS frameworks'... typically the consensus from the gurus is that there is not much of a case for a CQRS framework because the code is typically easy to implement per each project. I don't necessarily share this view but I think you'll struggle to find a current 'end-to-end' CQRS framework... that you can just rely on to do all the plumbing while you skip ahead to writing the business logic.
There are plenty of smaller frameworks for specific functions...like event stores, ddd structures, message buses, http apis, event feeds etc which can be wired together to deliver a 'CQRS' architecture.
Are probably the closest thing to what you need if you go that route.
NCQRS is a very opinionated heavy handed way to do cqrs. Lots of moving parts that often are not needed in most cases. I started with the framework a few years ago to help me understand the cqrs architecture but at this point people were already gravitating away for the reasons above.
If you do wish to commit to this 'framework' (ncqrs) I can possibly offer some direct guidance or do a post about how i'm using it in my project.