So far as I know, there are no C++ books dedicated to UE4.
I would suggest the following:
*Get a good background in C++ programming. Books by Stephen Prata (C++ Primer) for example should be a bonus.
*If you want to get game focused C++ training, I would recommend the game programming online courses from www.gameinstitute.com. (Disclaimer! I am not associated with this institute. Just took a few courses.)
*Another great resource is the book by Mr.Mike “Game Coding Complete, 4th Ed”. I refer to this book constantly:
*Before jumping head first into the UE4 rendering code, if you want a gentle intro to rendering, try Frank Luna’s book “Introduction to 3D Game Programming with DirectX 11”
Luna has a website for the code examples. Be sure to compile, run and dissect the code. Needs a Visual Studio 2010 environment though.
*UE4 code uses a lot of patterns. Singletons, component patterns etc. The following is great resource:
You need to be really comfortable with C++ before you jump into UE4 code. Without offence, do you have any previous programming experience in C++?