Why does OpenGL seem too complicated?

I have recently bought the book "OpenGL superbible 5th edition" in an attempt to learn OpenGL, my understanding of c++ is good coming from a java background, but my main problem is that this book doesn't explain ANY of the methods it is using with regards to OpenGL, so my question is:
Can anyone recommend a good book that they have experience with that teaches OpenGL effectively?
and if you know OpenGL, Where did you learn it?

Thanks in advanced.