After reading more of the posts I want to clear a few things up (perhaps I should update the first post as well).
First, reading books does not give xp toward anything other than reading and student.
Second, it can take sometime to get a library running if you just assign peasants. This is why I am doing these experiments so that we can figure out what skills should either be bought on embark or trained on site to kick start a library.
Third, military dwarves assigned to the library mostly discuss naturalist topics like foraging and water cycle. I have not seen them branch off into other topics yet, so I'm not sure how effective they would be at starting a library.
Fourth, it hardly matters if dwarves form a master/apprentice bond if the master is not highly skilled. The bonus from teaching/student skill is not very high either.
If you want to kick start a library, based off results so far, the best way would be to add a furnace operator, a mechanic, a record keeper, an appraiser, a pump operator, a military dwarf, and whatever medical/scholar migrants you have to their own individual libraries for a few years, then add them all together once they have branched out into all available topics and achieved a modicum of skill.
Conversely you can add them to a library all at once but likely the military dwarf would take the others on as apprentices which would not necessarily be the best since the military dwarf will teach primarily naturalist topics.
Edit: I should add that all the skills I listed for a starter library post embark are pretty easy to train (excepting of course medical/scholar skills which you would of course need to get from migrants unless you are breaking dwarves legs over and over).