I'd say buy two so you could customise one as the tower of Barad-dûr, but at $200/£170, that might be pushing it. That said - my god, Lego have pulled out all the stops for this one!
Standing at 28.75" tall, 8.27 inches wide, and 6 inches deep, this whopper of a Lego set has 2359 pieces in it - enough for the tower and a 9 inch tall Ent to go with it!
The tower inside has 6 floors detailed - from Saruman's Palantir room, to a Library, to an Alchemy room to make Uruk Hai bombs - and the set comes with an Uruk, an Orc, Saruman, Gandalf the Grey (complete with a Great Eagle), Grima Wormtounge and the brick-built Ent.
If your Wallet is ready, the set comes out in July.