Do you think that Hollywood is completely devoid of any original thought whatsoever? Does it seem to you like every movie is a remake, based on a TV show, video game, etc., or something that has already been done in another movie? Well, then then you're like me before I saw Inception.
Any description of the movie I try to give wouldn't do it justice, so I'll explain the plot in the simplest way possible. Leonardo DiCaprio's character specializes in entering into people's dreams and stealing their ideas. He has been hired to plant an idea into someone (inception), as opposed to stealing it.
As for the movie itself, the plot is engaging. It's a movie that you're really going to have to pay attention to in order to follow. The special effects are well done, and they fit well into the plot of the movie. The ending is great, because it causes you to wonder if it really is a happy ending or not.
Overall, if you want your faith in Hollywood at least partially restored, go see this movie. If you want to get caught up in an interesting story for 2+ hours, go see this movie. If you want to walk out of the theater feeling like you didn't waste your money, go see this movie.