OpenGL and graphics, in general, is a really vast domain. One book is not enough to cover it entirely. But drawing 2D graphics with textures and buffer objects opens the door to much more advanced stuff! In more detail, we have learned how to initialize and bind OpenGL ES to the Android windows with EGL. We have also loaded a PNG texture packaged as assets with an external library. Then, we have drawn sprites efficiently with OpenGL ES extensions. This technique should not be overused as it can impact performance when many sprites are blitted. Finally, we have rendered a tile map efficiently by pre-computing rendered tiles in vertex and index buffers.
With the knowledge acquired here, the road to OpenGL ES 2 is at a perfectly walkable distance! But if you cannot wait to see 3D graphics, Chapter 9, Porting Existing Libraries to Android and Chapter 10, Towards Professional Gaming, are your next destination to discover how to embed a 3D engine. But if you are a bit more patient, let...