The "Thinking in React" doc on the main React page, and their tutorial, were greatly helpful, and it was about 80% of my reference docs. I didn't bother with trying to interface with existing Backbone models, but your app may be too huge to rewrite (it still took me several months to rewrite from scratch, but it's a side project so it probably would have been a few weeks if full time).
That "js stack from scratch" repo is also very helpful in setting up the whole build.
That "js stack from scratch" repo is also very helpful in setting up the whole build.