GLFS is a rolling release book and is often rendered right after the last Git commit or batch of commits in the Git source. Currently, there are no releases besides the current one, which the version is named after the first four or five characters of the last Git hash.
GLFS can be obtained from the Github repository:
git clone https://github.com/glfs-book/glfs
You can update the source by doing:
git pull
Rendering works the same way as it does with the *LFS books. Read the included INSTALL.md for finding out what packages you need in order to render the book in the way you want to. README.md also provides information like rendering options you may want to set.
If you want to render the Systemd version of the book, for example, run:
make REV=systemd
GLFS has a list of packages which you can download. Please use the versions listed in the book unless you know what you are doing.