1. Async JavaScript: Build More Responsive Apps with Less Code http://www.amazon.com/gp/product/B00AKM4RVG/ref=kinw_myk_ro_title http://www.amazon.com/gp/produc

1. Async JavaScript: Build More Responsive Apps with Less Code http://www.amazon.com/gp/product/B00AKM4RVG/ref=kinw_myk_ro_title http://www.amazon.com/gp/product/B00AKM4RVG/ref=kinw_myk_ro_... Any serious JS dev needs to master async. 2. Functional JavaScript: Introducing Functional Programming with Underscore.js http://www.amazon.com/gp/product/B00D624AQO/ref=kinw_myk_ro_title http://www.amazon.com/gp/product/B00D624AQO/ref=kinw_myk_ro_... While the book uses Underscore, that's not its focus. A good understanding of functional programming and when it can be useful is a valuable skill.