I'd like to study more about tree grafting.know some helpfull books?

I recommend going to the library, and searching for any books on grafting or propagation. When you find the area, you see that they are all close to each other on the shelves. Grab a big stack, and flip through some. Once that have lots of photographs and diagrams are usually the most helpful. It's a very visual process, and a book that is all text is going to be harder to understand.