App Inventor: Create your own Android Apps, published by O'Reilly in 2011, is now available in PDF form here at appinventor.org. The links to the right get you to PDF versions of each chapter, or to a page with the PDF and accompanying video lessons. The book was written by USF Professor David Wolber along with App Inventor creator and MIT Professor Hal Abelson and Google engineers Ellen Spertus and Liz Looney.The book is designed for absolute beginners but also useful as a reference to programmers looking to add App Inventor to their arsenal.
The book is organized in a way to motivate learning. The first section walks you through the creation of twelve successively more complex apps that you can build and customize. Find something you'd similar to what you'd like to build and go for it. The apps section is followed by a separate "Inventor's Manual" section which explains programming and computer science concepts in layperson's terms. This section is organized by programming topic as in a traditional text.
Interested in building apps but don't have a year to learn Java? Teaching an introductory (CS0) computer science course to K-12 or university students? This book is for you!
The paperback version is a great companion to app building-- you can use the book to read the tutorial and save your screen for all of the App Inventor windows. Buy it cheap at Amazon!