It's more a matter of learning how you can use them in various ways, and also of really getting into the habit of thinking with deferreds. I've been using them for about 7 years (mainly in Python) and I'm still finding interesting new ways to think about them, new tricks, etc. [Disclaimer: I'm also one of the book's authors.] BTW, if you use AUTHD as a discount code on the O'Reilly site, you'll get 50% off the e-book price or 40% off a dead tree version.

Buy it and you'll find out... ;-)

I wrote this high-level piece of fluff as a taster for the Guardian's developer blog:

http://www.theguardian.com/info/developer-blog/2013/sep/17/d...

"If Doctor Who were a programmer, he'd use deferreds!"