What is the purpose of GPU Gems?
I mean like what is the purpose of this book and what they want to teach and will it be helpful regarding working with Rendering and Graphics in UE4?
If it will be helpful,there are 3 versions of this book GPU Gems 1,Gpu Gems 2,Gpu Gems 3, Which among these should I read?

These series are designed to show different functionality you can move to the GPU using shaders. Unless you’re planning to contribute to UE4 engine development, these probably won’t be of much use since UE4 shaders are compiled dynamically from our material instances. Understanding, generally, how shaders work is helpful, but being a master shader programmer isn’t that useful for using UE4 IMO.

GPU Gems shows how some of the best minds in both Video Games and Rendering industries have overcome the challenges that they faced while working on different projects. GPU Gems is a great resource for anyone who wants to learn more about advanced HLSL and rendering techniques but they are not tutorials. Also keep in mind that the GPU Gems are written for people who have lots of experience in their respective fields because they were written by similar people who want to share their ideas. This means that at times the information can be very complex to understand. In fact it’s more like reading a scientific paper(One could argue that is what it is) but with images that you might notice from your favorite Video Game or 3D Movies. Everything you see in the GPU Gems can be implemented into UE4 but this would be quite the task as the complexity involved is quite high. If you are new to UE4 and want to learn more about Materials check out the official documentation first before reading the GPU Gems as you will probably get more use out that information as it is UE4 specific.

@Sam Thanks a Lot!