Page "Sputnik Sweetheart" Paragraph 9
The book's major themes include loneliness and people's inability to truly know themselves or the people they love.
This is symbolized by the recurring metaphor of the Sputnik satellites orbiting at a distance from the earth.
As in The Wind-Up Bird Chronicle and Dance Dance Dance, Murakami uses ( or rather, suggests ) alternate worlds as a plot device.
He is considerably less given to or adept at wisecracks, maintains a respectable and stable profession as a schoolteacher, and is less self-confident and much more introverted and conflicted than any other Murakami protagonist.