This is Andy Lindeman's book (Philip De Smedt produced a similar one). Much better than the official RailsGuide on the topic. And very useful, especially when the alternative is searching for blog posts. I hope he earned enough from the book to want to do more. We need this kind of quality documentation.
If you're in a position to buy this book and support the author you should do so. Our team used it to do the Rails 4 upgrade, and we EASILY saved greater than the minimal $75 cost of the book.
Cool.<p>There was, of course, always the free Rails-provided upgrade guide:<p><a href="http://guides.rubyonrails.org/upgrading_ruby_on_rails.html" rel="nofollow">http://guides.rubyonrails.org/upgrading_ruby_on_rails.html</a>
I want to redo the cover. Think thats kosher? I have actually wanted to do it for a while now, before it was even open source. Too awesome of a book for that so-so cover.