There is no game withoud sound, so it should have chapter that deals with sound. The options for freepascal are: openal and sdl.

Also no game without some sort of collision detection.

Title suggestion:
Game Developement with Object-Pascal

It should minimal show
- available compilers
- 2D
- 3D
- Sound
- GUI
- File Acces - File Formats
- AI
- Collision (2D-3D)
- Game engine flow

Also i think classes should be used whenever posible showing classes with inheritance. (The Power of Object-Pascal)

The danger is that there are lots of topics needed for game developement and each of them justifies for its own book.

I would be willing to write a chapter on sound programming.