have you looked in the Book Shop section on this site?
There are some good 'how to' books on vr and nvr.
Then cds are also good value and, as it saves the answers, you can see how he is progressing and target the areas he has difficulties with. There are also some excellent games etc on teh web. a few miutes googoling turns up some brilliant stuff!
Check what type of vr questions are asked in your area as some (eg kent) only use 15 types, some of teh books show 50 types.
As for losing interest I would say little and often and treat the VR and NVR as puzzles.
If all else fails bribery canbe very useful........