I really love the Greatwinter Trilogy (Souls in the Great Machine; The Miocene Arrow; and Eyes of the Calculor) by Australian Science Fiction writer Sean McMullen. It's set on a planet that's wracked by a strange and mysterious call which hypnotically draws any mammals over 10 Kg to walk Eastward until they drown in the sea. The people of that planet have built a feudal society ruled by librarians that holds the patchwork villages and towns together. Advanced technology is stymied by a mysterious force that systematically destroys any electrical devices or large vehicles over 10 meters in length. Through it all, a very intelligent and determined woman has been figuring out the keys to these problems and is determined to rule the library system to save humanity— even if she has to use human enslavement to achieve her goals. It's full of rowdy and fun characters and I can't recommend it enough.