The safe box ships on a CD in a DVD case. I'll have to recheck but from what I recall the manual was a printed version included. The download can be burned to a CD for backup purposes and of course the manual is electronic.
Thanks to the randomization factor of creating the dungeons it's highly replayable. Additionally, the different difficulty levels adds to this. And then's there is the modding. Best thing to do is play the demo. The demo will also allow you to tinker around with some basic modding to get an idea of what to expect.