MMORPG for the single-player story enthusiast
Lord of the Rings Online is often maligned for it's "WoW-ness" (as in World of Warcraft) and it's true. Game mechanics are eerily similar in the two games, and that's to LOTRO's credit, as it feels familiar and easy to pick up for the novice or World of Warcraft convert. Although it shares a lot in common with its more popular cousin, LOTRO takes a different path than WoW, embarking instead on a story-based rather than mechanics-based game system.
Everything in the game is steeped in the lore, which is deep, rich, and abundantly available. The systems support the lore, taking class queues directly from quotes in the novels, and by eschewing the ability to campaign as an evil character or class. The story itself plays out in highly scripted and well-made sub-plots called books that culminate in instances that run parallel to the quest of the Fellowship, allowing you to support and be an important part of the lore without tossing it out the window.
LOTRO is very friendly to the single-player and explorer at the expense of the PVPer or Raid fanatic. Players who thrive on either of those mechanics are likely to be disappointed -- this is not the game for you. But these detractions don't take from the game, they merely emphasis the niche carved out by the game, and as a living, breathing world, LOTRO is infinitely more cohesive and playable than WoW. To each his own, that's for sure, and you'll find most players on LOTRO are WoW defectors (myself included) who found in LOTRO a surprisingly well crafted labor of love to Tolkien's labor of love.