How to download a copy of the CiviCRM User and Administrator Guide?
What follows are steps to download and view the User Guide offline using the MkDocs software. 

Caveats: this solution (a) requires some technical skill to set up, and (b) still requires a web browser to read (though not an Internet connection).


Install pip (python package manager)


OS X: brew install python
Debian/Ubuntu: sudo apt-get install python-pip python-wheel

Install MkDocs

sudo pip install mkdocs

Download the source files for the guide from GitHub. 

git clone https://github.com/civicrm/civicrm-user-guide.git
cd civicrm-user-guide

Run MkDocs

mkdocs serve

View through your browser at http://localhost:8000


More information about the process is available on the documentation page within the CiviCRM Developer Guide.