I've no idea if its any good and it's not a factory publication but I just came across this self-published one on Ebay. It might be a useful supplement to the official Italian manual for those of us who don't speak/read Italian.
http://www.ebay.co.uk/itm/Moto-Guzzi-Nu ... 2ec9266227
http://www.ebay.co.uk/itm/Moto-Guzzi-Nu ... 2ec9266227