PDF versions (including one in Kindle format) are available in the archives at https://bitbucket.org/alfonse/gltut/downloads
aptitude install p7zip
p7zip -d FILENAME
And for what it's worth, I was annoyed at installing a package, but it is a pretty slick compressor: .7z 10782763 bytes basis
.tar.gz 17423885 bytes +61%
.tar.bz2 16493028 bytes +53%