I have started playing Book I now when Book 2 is so close - doing this I discovered that I had massive problems using the Nvidia 195.36.24 driver, such as only being able to run the program in windowed mode.
Remembering that I have ran it previously nicely in fullscreen I didn't give up (I have got a new hardware setup pretty recently, still with nvidia though)
Trying going back to the NVidia 195.30 driver made the program go nicely again!
So, since seeing on these forums that some people seem to be running into similar problems - anyone having problems with the linux version and Nvidia graphics card, try to go back to a previous version of the nvidia driver (195.30 works fine for me.)
[edit - spelling mistakes]