The Middle-Earth Campaign Guide provides some important information and details for any player or GM of the MERP or Role Master systems (or any system set in Middle-Earth).
This set included a 24" by 36" full color map of Middle-Earth.
Inside the campaign guide there is plenty of detailed information, including: a full timeline of the history of Middle-Earth, guidlines and hints on the linguistics of Middle-Earth, a glossary of notes and terms, Maps depicting things like population centers, trade routes, prevailing winds and currents and so forth. The Campaign Guide even includes an English to Elvish dictionary, with notes on grammar and structure.
This source book was a compilation of previously available material from the Middle-Earth Adventure Guidebook, Volume I & II.