Yup - I wrote a similar book (Google is your friend if you want to find it - don't wanna steal publicity here). I haven't sold that many but the process of writ

Yup - I wrote a similar book (Google is your friend if you want to find it - don't wanna steal publicity here). I haven't sold that many but the process of writing it and giving support has been really cool. I learned a ton in just writing the book and currently I'm working on my next one (on AngularJS + Rails). Funnily enough, I've also been thinking about giving away Upgrade to Rails 4 for free through Leanpub. Might do that sooner or later.