Chris Strom and I have finished our e-book on Backbone JS: "Recipes with Backbone". It is now available at http://recipeswithbackbone.com for $24.
The book is targeted at the intermediate to advanced level backbone developer, but that's not to say beginners won't get anything out of it. To quote the site:
- This is not the definitive guide to Backbone.js.
- This is not an introduction to Backbone.js.
- This is the book you read after you read the tutorial.
- This is Recipes with Backbone
- Preview the table of contents
So if you want to learn more about backbone js, buy it!