There were 3 print editions of the RKMs, and the number of volumes in each edition varied. The third edition covers up to the A3000 and consists of Includes/Autodocs, Devices, Libraries, Hardware Ref Manual, and the UI style guide.
The Dev CD v2.1 includes the only digital release of the RKMs (amigaguide format, I think) and NDKs up to 3.5. The 3.9 NDK can be found
here
