what do i need to start building a java game from scratch?

I'd start with a tutorial

Cheers,
Dian

I recommend your cousin start with 2d(2 dimension) game and understand the theory of game.
There are many terms in making a game. People may store the picture of main character of game into a square of photo. They may call it sprite. The background of the character may be transparent or at the same colour of the background.

After I have read the index of your book, I think your book seems good enough.
But your cousin may need another book to teach him the fundamental knowledge of Java.

People may write game with Swing and run the game in computer.
Some people may write the game with J2ME and they may run the game in certain mobile phone or under J2ME toolkit in Windows.

He may follow the book and use Java Swing to write Java game.

Some change in wording of my option.
I recommend your cousin start with 2d(2 dimension) game and understand the mechanisms behind the computer game. After he has be skillful in writing game, he may read books for writing 3d game if he wants.
3d game may need more calculation in Maths. Matrix may be used.