No problem man, anytime!
book should be the first one you read as it will give you a good understanding of how the core functionality works. GPU Gems and GPU Pro are advanced techniques that build upon the core functionality of a game engine and/or rendering setup.
All 3 of these will help you gain the knowledge to create your own rendering solutions, each one being more advanced than the next. Once you have a good understanding of the core functionality taught in “Computer Graphics: Principles and Practice”, the algorithms and techniques in GPU Gems & GPU Pro will be easier to create and implement into your rendering solutions.
I would personally start with Computer Graphics: Principles and Practice first and read GPU Gems on the side as well since they are free, then get GPU Pro at a later date. They are really expensive books so it might not be easy to buy them both at once. 