Books Used Last Session (July 2):
Players Handbook (1st edition) -- miscellaneous stuff (spell description, equipment prices, etc.)
Dungeon Masters Guide (1st edition) -- miscellaneous stuff
Monster Manual (1st edition) -- assorted monster stats
Monster Manual II (1st edition) -- to check the move rate of a domestic cat (for a PC's familiar)
Unearthed Arcana (1st edition) -- to check the characteristics of a garrotte (which the player ended up deciding not to buy)
RuneQuest Cities -- for urban random encounters
Accessories -- DM Screen, Dungeon Masters Adventure Log
This was the first time in the campaign to date that the MM2 and UA were referred to; previously it had always just been the "big three"