The sleepers are Amtrak's version of first class. A single sleeper compartment contains a fold down bunk above two seats and a table beside a window, all in a private compartment. The lower seats can also be converted into a second bunk. Sleeper class passengers get complementary coffee, and do not have to pay for eating in the dinning car.
Very nice, but a bit pricey, especially when you're traveling alone. Besides, I found I spent most of my time in the lounge car anyhow, talking with other passengers and taking in the view.