If you're avoiding Lord of the Rings because of its length. Read "The Hobbit". It's more interesting in terms of story, (LOTR is good, but it's written partially as a "History", so it isn't well paced).
Read the "Earth Sea" trilogy. 3 (technically 4) fantasy books which are very interesting and have an extremely unique take on magic (The half-baked, horrible written Eragon books stole most of its ideas from Earth Sea).
H.P. Lovecraft short stories are always an interesting quick read. And I'm not talking about Cthulhu, the others, like Rats in the Walls, and Polaris are fascinating (and very intriguing).
Someone else mentioned the Redwall series. Yes, GREAT books, the plots get reused and a little anti-climatic in the most recent handful (like Doomwhyte, for example), so I would suggest reading them in order written. I would suggest Redwall, Martin the Warrior, Mattimeo, Luke the Warrior, The Taggerung, Mossflower, and Outcast of Redwall as the most interesting, best written, and my favorites. The Taggerung is my absolute biased favorite (with Outcast in close 2nd).
if you like Animal Farm, read "The Great Gatsby"
Now for relatively unknown, but FANTASTIC books (seriously, read them!).
The Ordinary Princess
The Princess and the Goblin, and its sequel The Princess and Curdie (and any other George MacDonald stories are genius).
Watership Down
The Screwtape Letters is always interesting, and while, yes, it's a very Christian book, written by a very Christian author, it is also very dark, as the premise is one Evil Demon writing letters back and forth between another Evil Demon about a man they're trying to destroy, so it's a very interesting and slightly off-putting read.
The Thief (by Megan Whalen Turner) my favorite book of all time. It's a bit young, directed towards the 14-18 year crowd, but it still holds up, in my opinion.
