Hi Sam First of all congratulations on the new edition, I know it must have been a lot of hard work to refactor the book with the changes made in Rails 4 but I would like to make a suggestion for an addition to the book.
ActionController::Live is a major new feature of Rails 4 that will have a major impact in the Rails world and it’s ommission from the book is a major oversight. Live streaming would majorly enhance the Depot application and it has a major impact on a production server as regards top performance, server resources needed and what rails servers should be used if implementing ActionController::Live
It would be fantastic to see how you would implement ActionController::Live to say update available quantities or show a count of number of books sold today. I can think of many examples where live streaming would be a good fit but most importantly your opinions on where and how it should be used and where it is not a good idea to use it would be an invlauable section.
I appreciate that re-working the book to change what was already there must be a lot of work but it is equally important to include the newer features available.