This is the the 2nd edition, released March 27, 2015, in PDF, epub and mobi (Kindle) formats.
The PDF file has a bookmarked table of contents for easy navigation (make sure you turn bookmarks on in your PDF reader).
The epub version looks very good on (for example) iOS devices like the iPad. (The easiest way I've found to transfer it to iOS is using Google Drive; you might have to go through two levels of the "Open In" command).
The easiest way to transfer the mobi file to your Kindle device is either directly using a USB cable, or by emailing it via Amazon
Before buying, make sure you try out the free sample which contains the first 100 pages of this book in all three formats, so you can be sure you want it and that it works on your intended device: Free Sample
The book's examples are available on Github
This ebook is not copy protected so you can easily place it on all your devices. However, it is copyrighted material -- please encourage others to purchase their own copies.