I found this book but it talks about an SDK created by the author rather than pure simple OpenGL ES 2.0; this sounds more like a commercial to me than a good book for programming. I would like to start with just OpenGL ES 2.0 without talking about anything else: can you give me a good advice on this? A good book or on-line resource.
I'm also interested in cross platform development with OpenGL ES, in particular Android and iOS.