Several people have asked (waves hi to Aaron) how to grab the latest Swift book as a PDF. My copy of the Prerelease book is encrypted. I assume yours is too. You probably want to do something like this not this, but I haven’t fully tested yet because I’m knee deep in a chapter about printing and mirroring.
If you can’t fetch with site sucker, just wget from the command line:
wget -r -l1 --no-parent https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/index.html
I’ll leave the whole “set up calibre page layout” thing as an exercise for the reader but if you have some good ways to produce good PDF output please drop a note.