Here's a glimpse of RoK:
Virtually a chapter on every country in Hyboria, including major locations/sites, the people, a map breakdown of the region, their religions, as well as some adventure hooks for each country drawn from REH writing.
I noticed that Mongoose has gone beyond the works of REH to flesh out some of the countries, which I for one am grateful they are all in one place instead of spread amongst so many writings.
There is a Game Mastering section at the end, which has even more adventure hooks and new feats. I'd say that the feat section seemed like it was a little thrown together with little introduction.
All in all, I found the book very informative (from my grazing), but left me wanting more. When is the
Pirate Isles coming out?

And more adventures!!
Ken