So covenents says these books, the "roots" and "branches" of the arts exists. My question is, which arts have Roots, and which have branches? Also, what would the levels and qualities of these books be? Finaly, how much should they cost (in vis)? Just looking for opinions...
I could not even hazard a guess as to which Arts are covered, but as for level and quality: roots are primers capable of getting anyone high enough to train apprentices, so I would go with level 5, maybe 6. Since these are considered THE primers, I would put the quality up to 15 or 18. Granted, a 5 / 18 summa is still considered "vain", but quality over 18 on such a low level book is useless.
I am not sure what Bonisagus' field was, but I'd guess he was decent at Vim. From what I recall, his base book quality is 12. However, resonance allows this to be boosted a little without suffering loss of level, so let's say it's quality 15. Since no Art summa has yet been written whose Level+Quality exceeds 40, the level of such a masterpiece would not exceed level 25. Was a score of 50 in Vim appropriate for old Bones? I guess.
Using a book total of 40 as a "hard limit", it's unlikely any branch has a level exceeding 30.
This is all conjecture, of course, but that's what you wanted.
Heh! Thanks Rex, I had been looking for input from people OUTSIDE our gameing group, but your points make sense. 
So which eight have roots and which seven have branches? I guess we could determine randomly, but perhaps there is a more logical way to go.
Deliberately, if you character years to write a great book, there is nothing stopping him, but if he is more likely to want a great book, then it is available.
This is one of those areas of deliberate ambiguity in the rules.