I'm currently busy coding the 3D renderer interfaces and the object model (mainly serialization) at the moment. Due to my lack of 3D renderer coding knowledge, I searched for books covering that topic.
The book I found most interesting (and bough eventually) is
3D Game Engine Design 2nd Edition by David H. Eberly
It covers nearly every topic you need for implementing a modern 3D renderer.
The source code for Eberlys Engine "Wild Magic" comes with the book and is always worth a look if you want to know implementation details.