To get an approximate feel for medieval life, here are a few books we would highly recommend. They've been immense help in fleshing out Frilond and should aid any player.
Briggs, Katharine. An Encyclopedia of Fairies: Hobgoblins, Brownies, Bogies, and Other Supernatural Creatures. NY: Pantheon Books, 1976.
Davis, William Stearns. Life on a Medieval Barony. 2nd edition. NY: Harper & Row, 1953.
Frazer, Sir James George. The Golden Bough: A Study in Magic and Religion. abr. ed. NY: Macmillan, 1922.
Gies, Joseph and Frances. Life in a Medieval City. NY: Harper & Row, 1969.
_______. Life in a Medieval Castle. NY: Harper & Row, 1969.
Gravett, Christopher. Norman Knight 950-1204 AD. Vol. 1 of Osprey Warrior Series. London: Osprey, 1993.
Haskins, Charles Homer. The Renaissance of the Twelve Century. Cambridge: Harvard UP, 1927.
Nicolle, David. The Normans. Vol. 9 of Osprey Elite Series. London: Osprey, 1987.
Russell, Jeffrey Burton. Witchcraft in the Middle Ages. Ithaca, NY: Cornell UP, 1972.
Tigner Holmes, Jr., Urban. Daily Living in the Twelfth Century: Based on Observations of Alexander Neckam in London and Paris. Madison: University of Wisconsin Press, 1952.