I sort of know this area.... There two separate paths -- realtime or non-real-time.

For non-real-time there is: http://www.pbrt.org/

For real-time there is this: http://www.realtimerendering.com/

Neither book gets into the details of the specific API, they are theoretical.

Real-time techniques change nearly complete about every 10 years because GPUs get faster and render more techniques possible and obsolete the older less good looking techniques.