I mentioned earlier, that in June Microsoft released a free preview of Kraig Brockschmidt’s Programming Windows 8 Apps with HTML, CSS, and JavaScript book, which although had only 4 chapters, proved to be a valuable source for developers using JavaScript to create Metro style applications for Windows 8. Now MS Press published the second preview of this book with a total of 12 chapters. The new chapters are:
- Chapter 5: Collections and Collection Controls
- Chapter 6: Layout
- Chapter 7: Commanding UI
- Chapter 8: State, Settings, Files and Documents
- Chapter 9: Input and Sensors
- Chapter 10: Media
- Chapter 11: Purposeful Animations
- Chapter 12: Contracts
The first preview was 158 pages, the second 537, and when all 17 chapters of the book will be ready for the Build at the end of October, it will be heavy 
You can download the second preview for free:
- PDF e-book (13.5 MB)
- Companion content (source codes and videos) (64.9MB)
If you are not interested so deep in this topic, or you just start Windows 8 development, you may be interested in the Beginning Windows 8 Application Development from Wrox. In this book 70 pages are about JavaScript Windows 8 development, touching similar topics like the MS Press book, but specially for beginners. Although this book will be officially released only next week, you can preorder it from Amazon.
I learned it. I share it. 