is it possible, and how?
Only old guides are available for download at the moment, and until the wiki maintainers find a way to easily convert from wiki to PDF or other formats.
You could use a site downloading program such as GetLeft.
Hope this helps.
PLEASE! Don’t download the whole wiki with a site leecher!!! That will bring the wiki server on it’s knees…
Instead, If you update the following page (warning, big download), It’ll be almost everything!
If you look at the code (edit button) you’ll see how easy it is to make the manual into one big document:
http://mediawiki.blender.org/index.php/Manual/Complete
The only “problem” is the navigation bars, but that’s only minor. I will ask the docboard friends if we can update this, then run some cleaning code on it (i.e. remove navigation and other wiki stuff) and then save it as a PDF.
or buy the book 
PLEASE! Don’t download the whole wiki with a site leecher!!! That will bring the wiki server on it’s knees…
I second that, a spider/leech/bot in inexperienced hands can be as damaging as a DOS (Denial of Service) attack, and will even get your IP address banned from many servers. In the U.S., the consequences for suspected DOS attacks may be more serious than that, given today’s hysterical climate.