Set in the world of The Silmarillion, The Hobbit, and The Lord of the Rings, MERP allowed players to run campaigns in any era of Middle-earth's history—though the default era was the year 1640 of the Third Age, approximately a millennium and a half before the War of the Ring in a time when Sauron is only just starting to rebuild his power. The southern kingdom of Gondor is recovering from civil war, while the northern kingdom of Arnor is under seige from the Witch-King of Angmar. The Great Plague has just ended, drastically reducing the population in northwestern Middle-earth but opening up new opportunities for the survivors. Sauron remains in hiding, but his servants, the Nazgûl, gather forces under his banner. The lands are less settled but also more free, and Elves, Men, Dwarves, and even Hobbits might find adventure.
Because its setting was relatively little-detailed by Tolkien, MERP was allowed a great deal of creative freedom and developed its own mythos derivative but distinct from Tolkien's, with a close attention to the languages and cultures of Middle-earth.
MERP went out of publication in 1996 and the license reverted to the Tolkien Estate. Other Middle-earth RPGs have since been published by Decipher (The Lord of the Rings Roleplaying Game, 2002-2005, tying into the Peter Jackson movies) and Cubicle 7 (The One Ring, 2011-present, taking place shortly after The Hobbit).
The game had a thriving fan community rallied around the fanzine Other Hands, which ceased publication in 2001. Other Hands was succeeded by an extensive fan module project and the current webzine, Other Minds.
Middle-earth Role Playing provides examples of the following tropes:
- Adaptation Expansion: And how. MERP just about doubled the information available on Middle-earth from what Tolkien provided, and that's no mean feat. For example, they provided unique and fleshed-out cultures for the "enemy" Men such as the Easterlings and Southrons.
- All There in the Manual: Information on the names on an early map was found only in an unpublished gazetteer, which thankfully can be found in several places online.
- Animal Motifs: Seven of the nine Nazgûl have a helm based on some sort of animal (Akhôrahil and Ren do not). Khamûl's is dragon, Dwar's is a war-dog, Indûr Dawndeath's is an elephant (or more precisely, a Mûmak), Hoarmûrath's is a polar bear, Adûnaphel's is a falcon, and Ûvatha's is a bat. The Witch-King has a helm in the shape of an octopus because the artist mistook the Dragon-helm of Dor-lómin on the cover of Unfinished Tales for the crown of Númenor, which she assumed was a cephalopod (Númenor being a seafaring civilization; in fact, the crown of Númenor was a simple winged helm).
- Big Bad: Sauron, naturally—though in the canon setting of T.A. 1640 he's in hiding and is The Man Behind the Man for his Dragon, the Witch-King of Angmar.
- Call a Rabbit a "Smeerp" / Gratuitous Elvish: The modules often used the elvish names of common animals/objects, even in non-flavour text.
- Early Installment Weirdness: One of the first adventure modules, The Court of Ardor, centered on a cult of Morgoth-worshiping dark elves in the far south of Middle-earth. This was ignored by later products.
- Fantasy Counterpart Culture: MERP's take on the Easterlings was very strongly based on Mongol horsemen. (Ignoring the fact that Tolkien explicitly notes they used horses mainly for pulling wagons and chariots and rarely fielded cavalry.)
- Functional Magic: The sourcebook Gorgoroth includes an in-depth description of the Sammath Naur (Sauron's forge and laboratories inside Mount Doom), and how the Dark Lord used its capabilities to create the One Ring. For example, one of the six Rooms of Tempering imbued the Ring with protection from decay and corrosion by focusing time energy upon it. Any person caught inside the chamber when it is activated ages at a rate of one thousand years per second – even Elves fade and die after an hour (3.6 million subjective years) of this treatment.
- Half-Human Hybrid: In addition to Tolkien's half-elves and half-orcs, MERP introduced the Umli, a race descended from the union of Men and Dwarves, who live in the Northern Waste.
- Hobbits: Naturally. They're a bit less soft and complacent than they are in The Lord of the Rings, though—the Shire has only been settled for about 40 years, and a lot of Hobbit clans are still wandering in the Wild.
- Lady of War: Adûnaphel, the only female Ringwraith.
- Poison Is Corrosive: Supplement Rivendell: The House of Elrond. One of the poisons listed in the 9.1 Herbal Chart table was Camadarch Acid. When mixed with alcohol, it inflicted Heat critical hits on the victim.
- Quirky Miniboss Squad: The nine Ringwraiths, each of whom was given a distinct backstory and personality.
- Red Oni, Blue Oni: Marcho and Blanco Fallohide, the co-founders of the Shire. Marcho's aggressive leadership gathered the many Hobbit clans together, while Blanco's soft-spoken diplomacy convinced King Argeleb of Arthedain to grant them the Shire to live in.
- Treasure Room: The beacon tower of Calenhad in Gondor has an Upper Treasury room. It's filled with gold and mithril coins, various rare and valuable goods and the Tower Captain's collection of magic items, including two magical swords and a pair of magical boots.