I'm wondering how many different titles might be extant in the Order at large in those topics of interest to at least a few members. If I go with the following broad-brush assumptions, I get about 420 spread across maybe 30 topics of interest.
Members of the Order (past and present): 2500
Members who might write a barely acceptable book: 50% (1250)
Those that followed through: 50% (625)
Average number of books per author: 1.7 (1062)
Titles lost due to war, Winter, accident, etc.: 40% (424)
I'm not including any lab texts or Mystery Lores. Also, I'm assuming that especially low quality titles are very rare and vanish quickly.
So maybe 3-20 titles for a given topic, depending on interest. Does this seem reasonable?
Seems like there wuld be a lot more studying from vis and Practice going on than I had previously guessed at.
I'd say fewer writers, say 5-10%, but more prolific, at least one or two summa and dozen tractatus each (that's less than 5 magus-years, not much compared to the lifespan of a magus). I'd also probably lower the loss rate to 20-30%, but that has only a very minor effect. I'd agree with 30 main topics, including the 15 Arts. This means something around 5-10 summa and some 60 tractatus/topic. Enough to get Abilities into the mid teens and Arts into the high 30s on study alone.
Besides, those are titles, not books Most titles will get multiple copies. As such the loss of books due to war would be lower IMO, and consists of subpar books that nobody wanted to read about anyway. Low quality books, given the rules (not reality, mind you) can see a surprising turnout rate as well, since a low quality tractatus is still useful and way less dangerous than lotss of vis for an undefined gain when you are old.
Members: I've pondered this recently. I can give you my numbers if you're really interested, but based on my assumptions, I get less than 2,000 magi in the order over the course of its history. But the Schism war confuses everything, because I don't have a quick model for a massive population drop. Given that we know it happened, I could definitely see 2500 as a reasonable guesstimate.
Might Write: I'm afraid I find your guesstimates about who could write a reasonable book a bit tough. For summae, and when talking about arts, it seems like almost any specialist magus can write an acceptable summa on his area of expertise. (I'm not sure how popular Q6, L25 summa would be in the order, but they're easy for a master to write, if said master is willing to take a year.) So it'd really be a function of what percentage of magi reach old age.
For tractati, on the other hand, the limiting factor to whether the book is worthwhile is Com, not specialization. A Strong-Writing or Mythic Com author is going to be in demand in every topic, whereas Grand Archmage McFlame, known for his unwillingness to explain to people who don't "get it", may be able to write 10 different Ignem tractati, but nobody will want to read any of them. So the limiting factor here is what level of Com/Strong Writer you consider necessary, and how large a population think has that level. I would argue that 50% is entirely too high an estimate.
Average books: Again, I think we can't clump summae and tractati together here.
When Archmage McFlame writes his Q3, L25 magnum opus, he's going to take at least a full year to do it. Even those Inky Fingers Ex Jerbiton is likely to have to put several seasons into it. And these pretty much have to be late-career books, since a summa's value is tied directly to the level the writer has in the ability in question. So it's likely that many magi die before they reach the point that they could write a summa of interest to the world. And, if we buy the way the RAWs implications work, it's at least suggested that by the age where magi are likely able to write such masterworks, they'll have some interesting Twilight scars, be embroiled in politics, etc, etc. I'm sure some manage to find the time to publish multiple summae, but my gut is that more authors will write a single summae in their life than 2, putting my guesstimate average for summae down nearer to 1.
As for our tractati authors... well, tractati should be all over the place. They take a season, and even Noob Ex Misc can write a servicable one in his first year after gauntlet. I'd say that someone writing only 1.7 over the course of their career is entirely too low.
Misc: There's also an interesting question, I think, about what books magi write. Are the libraries of the order dominated by books on techniques rather than forms due to how most magi consider technique study more valuable? Would any magus ever write a tractatus on Hunting?
If I have some time this weekend, I'll ponder my previous thoughts on demographics of the order (For example, what percentage of magi I think have Com +3 or Strong Writer?), and see what sort of book population numbers pop out.
We do have one model in recent history. The Holocaust. Some esitame that the Jewish population of the world would bbe roughly twice what it is today if not for the Holocaust.
And yeah, Schism War does make things confusing, especially since we have no numbers fro the population before and after. Diedne was a very large house, and the Tremere and Flambeau suffered great numerical losses.
But anyway, I figure that the esitmate is 1500 magi in 1220. And that's after 500 years and a schism war. I think 3000 is a safe esitmate if not much more. Basically I am saying that, of all the magi since the founding 500 years ago, half of the magi who ever lived are alive today (1220 today that is).
Then again, I estimate less than 100,000 magi in the year 2009
One quibble: here are the numbers from each HoH book:
Bonisagus: 52 Magi Bonisagi, and 29 Magi Trianomae
Ex Miscellanea: 180 (est.)
Mercere: 12 magi, 150 Redcaps
That totals to 1090 gifted, 1240 if you count the ungifted Redcaps. (Since the books referred to in the OP are likely mostly on the arts, I'd tend to leave the redcap count out.) So if we use your "1/2 total are alive" rule of thumb, 2200 would be a reasonable guesstimate.
Counter quibble. The main rules book states flat out that there are 1500 magi in the Order as of 1220. I will look it up later.
And yes, I include Redcaps. They can write books on Magic Theory, Lore, and mundane topics. Ungifted folks count as people too y'know
I don't know where I was pulling my numbers from, but ArM5 page 9 says there are about 1200 members of the Order of Hermes. So I have to totally withdraw my argument. I just favor a slightly larger Order of Hermes I guess. But where did I get that number from? Was it in the 4th edition Mysteries under the section that discusses a small, medium, and large Order?
Which is a HUGE part of the reason why we added the "Greater Tractatus" variation which adds a bonus based on the writers score in the subject(1/5 for Arts) while doubling write time. (and is included in the same limit for number of tracts that can be written)
Meaning that if grand old archmagey starts writing these in his elder days, the demand will likely be HIGH, because so also will the quality unless his Com is extremely low.
This is an option i would simply suggest any and all to use.