If you are a developer or would like to dip your toe into the exciting world of app development then you will definitely want to look into Anwar Ludin's latest book, Learn BlackBerry 10 App Development: A Cascades Driven Approach.
The best part is that Apress have made the book part of the ApressOpen collection. You can download and share the ebook for absolutely nothing. If you're someone who prefers the paper-and-print approach then you can still order the print book from Apress as well.
The book has been reviewed by members of the BlackBerry Developer Relations team to ensure that it's top notch. If you want to move on to more material, there are resources on Anwar's website (http://www.aludin.com).
More information / Purchase / download BlackBerry 10 App Development from Apress