As you might know (or I hope you do by now), Office Web Add-ins are the new thing. And if you have recently started a project in this new paradigm, you know that it is quite different from Office COM/VSTO/VBA based coding. There is a little bit of a learning curve and some of the new code patterns (namely async) make doing things “the old way” not quite possible. As such this can make getting your head around this programming model a tad tough. And then there is JavaScript too. 
One of my colleagues, Michael Zlatkovsky (a member of the Office.JS development team at Microsoft) is writing a book: Building Office Add-ins using Office.JS.
I have had an opportunity to read this book and believe it to be a great resource to understanding the new model. Some of the best parts of the book are where he covers the concepts behind the model, its use of async (and why), how to get around some of the challenges of async with Promises (great chapter), the way to use the Office context objects with some great code patterns, and much, much more.
Michael’s companion website is a must to bookmark as well. Check it out: http://buildingofficeaddins.com.