Don't think there is any such book specifically for UE and its source. But there's a lot of good books on realtime rendering and graphics programming in general.
GPU Gems, Shader X and GPU Pro are good series for learning specific graphics programming techniques.
It's fun to explore the source though, and NVIDIA has some cool experimental branches of the engine with their stuff integrated.
https://github.com/NvPhysX/UnrealEngine
GPU Gems, Shader X and GPU Pro are good series for learning specific graphics programming techniques.
https://developer.nvidia.com/gpugems/GPUGems/gpugems_pref01....
http://www.realtimerendering.com/resources/shaderx/
For a general game engine overview: Game Engine Architecture by Jason Gregory (Naughty Dog)
Game Programming Patterns: https://www.amazon.co.uk/Game-Programming-Patterns-Robert-Ny...
Realtime rendering overview: https://www.amazon.co.uk/Real-Time-Rendering-Third-Tomas-Ake...
Related math: https://www.amazon.co.uk/Math-Primer-Graphics-Game-Developme...
Other recommendations:
http://mrelusive.com/books/books.html
http://fabiensanglard.net/Computer_Graphics_Principles_and_P...
It's fun to explore the source though, and NVIDIA has some cool experimental branches of the engine with their stuff integrated. https://github.com/NvPhysX/UnrealEngine