At this point in our journey through the Android API, it is worth taking stock of what we know. We can lay out our own UI designs, and can choose from a wide and diverse range of widgets to allow the user to interact. We can create multiple screens, as well as pop-up dialogs, and we can capture comprehensive user data. Furthermore, we can now make this data persist.
Certainly, there is a lot more to the Android API still to learn, even beyond what this book will teach you, but the point is that we know enough now to plan and implement a working app. You could get started on your own app right now.
If you have the urge to start your own project right away, then my advice is to go ahead and do it. Don't wait until you consider yourself "expert" or more ready. Reading this book and, more importantly, implementing the apps will make you a better Android programmer, but nothing will teach you faster than designing and implementing your own app! It is perfectly possible to read this book...