This book is written for people having a reasonable experience with Java. I was able to breeze through this book in a couple of hours and "got it" what Android platform is about. Most of the book is about developing a Twitter App with each chapter taking the application gradually to the next level. Don't let that fool you. Each and every concept about Android ranging from the UI controls, File System, Database, Services, etc, are thoroughly explained. The book ends with chapters on the Android Interface Definition Language and the Native Development Kit. These concepts are important to know when dealing with Interprocess Communication (aka cross-application communication) and for accelerating performance and are thoroughly covered.
If you are wanting to learn Android in a hurry and want to finish in a couple of weekends, this is the book to go for. Otherwise, just go through the official documentation and spend months trying to write a decent application.