Let's investigate the inner-workings of your Arduino. It appears to be a simple machine, but it is not. Much effort has been invested to make it easy to learn and use. Unfortunately, these good intentions can mask some of the Arduino's underlying capabilities. You suspected that there was more, much more, under the simplistic veneer.
You were right.
This book is about how Arduino actually works. The Arduino is a successful composite of design decisions that has evolved over time. By giving you a more in-depth understanding of the complex technologies involved, you will see the Arduino "internals" as elements to be changed and re-arranged to suit your design goals.