I would immediately purchase a DRM free PDF edition of this book, if such were available. I find that's the best format for easily moving between study sessions

I would immediately purchase a DRM free PDF edition of this book, if such were available. I find that's the best format for easily moving between study sessions on my iPad and experimentation on my laptop (e.g. copying code snippets into a REPL or editor). I've been using node.js since early 2010, but I find it helpful to read books written by a platform's expert developers, as they tend to provide insights and demonstrate helpful patterns of which I was previously unaware. I'm not interested in buying (and won't buy) a printed copy or a DRM'd digital edition.