Q:

SF novel with "keepers of knowledge" who have to answer any question they're asked, but everyone else has to answer the questions they ask

A couple of years ago I read the first two novels in a series about a post-colonization world where there was a group of people whose job was to carry information from one town to another.  The rule was that people could ask any question they wanted of these people, but also had to answer any question of these people. The group maintained a library that was the "sum of all knowledge" and members had to keep, and archive extremely detailed diaries to add to that knowledge.  
Main character was a female keeper of knowledge. 
The society was clearly divided along lines of technology.  We learned in the second novel that satellite weapons were continually scouring the badlands and that there were an aristocracy who called themselves the "crewe".  
I think it was a female author.
I'd like to read the next/last novel in the series, but can't remember either title or author!

A:

Well I appear to be 4 years late but this is definitely The Steerswoman Series by Rosemary Kirstein.
The main protagonist is Rowan - a woman who is a Steerswoman - who travels the land collecting and disseminating knowledge. Every Steerswoman follows the rule that they must answer any question people ask (to the best of their ability) but also require that any question they ask must be answered truthfully. They are attempting to collect and understand all knowledge.
From Goodreads:

Steerswomen, and a very few Steersmen, are members of an order dedicated to discovering and disseminating knowledge. Although they are foremost navigators of the high seas, Steerswomen are also explorers and cartographers upon land as well as sea. With one exception, they are pledged to always answer any question put to them with as truthful a response as is possible within their own limitations. However, they also require anyone of whom they ask questions to respond in the same manner, upon penalty of the Steerswomen's ban; those under the ban do not receive answers from the steerswomen.

The land is populated by the general population, Outskirters, Wizards and Goblins.

The Steerswomen come from the general population and give and take knowledge freely until someone refuses to answer a question. This brings them into conflict with the Wizards who refuse to answer questions about their power. The Steerswomen are a group who maintain The Archive - a collection of knowledge - and are led by The Prime.
The Wizards are a tiny number of people who have enormous powers.
The Outskirters are barbarians who live in scrubland on the edges of civilisation.
The Goblins are creatures that attack humans

Big Spoiler 1:

 The heroine Rowan becomes interested in some jewels that are found in a strange widely distributed pattern. Eventually we discover that they are the remains of a satellite that has de-orbited but her search for understanding brings her into conflict with the Wizards who control the satellites

Big Spoiler 2:

 The reader comes to understand that the Wizards are descendants of the crew of the colonisation ship and are the only people who have "scientific" knowledge (e.g. Chemistry / Physics) rather than the type of knowledge collected by the Steerswomen.

Big Spoiler 3:

 Later books allow Rowan to discover that the habitable area of land is small but growing and that it was much smaller in the past. It is being made larger by the Wizards magic (actually orbital satellite weapons) which are being used to exterminate the Goblins. The Goblins are actually indigenous, intelligent local lifeforms and the satellites are scorching the ground to increase the ability of terran flora and fauna to expand.

The four books are:

The Steerswoman
The Outskirter's Secret
The Lost Steersman
The Language of Power

Be aware that books 1 & 2 have been published as one book under the title The Steerswoman's Road.

A:

I believe the series you are looking for may be The Snow Queen Cycle by Joan D. Vinge.
From Goodreads:

The imperious Winter colonists have ruled the planet Tiamat for 150 years, deriving wealth from the slaughter of the sea mers. But soon the galactic stargate will close, isolating Tiamat, and the 150-year reign of the Summer primitives will begin.
Their only chance at surviving the change is if Arienrhod, the ageless, corrupt Snow Queen, can destroy destiny with an act of genocide. Arienrhod is not without competition as Moon, a young Summer-tribe sibyl, and the nemesis of the Snow Queen, battles to break a conspiracy that spans space. Interstellar politics, a millennia-long secret conspiracy, and a civilization whose hidden machineries might still control the fate of worlds all form the background to this spectacular hard science fiction novel from Joan D. Vinge.

