The narrator of the story, K. (another hint of Murakami's love of Kafka), is in love with an ex-college friend, Sumire, who in turn is in love with her new boss, Miu, who isn't in love with anyone, not even her husband, because of a strange event in her life fourteen years ago. After Sumire flies off to Europe on a business trip with Miu, K. gets on with his life, as most Murakami male protagonists do, with classical music, simple home cooking, enjoyable but meaningless affairs and the odd drink too. Then he gets a phone call from Europe, and everything comes crashing down...
The central premise may seem like an ordinary love triangle, but the writer turns it into something more. The three main characters are all loners who have trouble defining their identity, and the relationships they enjoy with each other are a way to start to understand what they want. K. serves as a sounding board for Sumire's constant inquisitiveness, and Sumire helps to get K. to see things from another's point of view, something he's not always very good at doing by himself. When Miu comes along, Sumire is instantly smitten and temporarily abandons her bohemian lifestyle and attempts to become a writer, following Miu to see where the trail will lead.
The connections the three characters have are strong, yet it is always clear that they are ultimately temporary, likely to end soon, and this is one of the writer's key points. In life, people are very much like satellites; while we may occasionally cross paths and accompany each other for a while, we are all alone in the end, trying to understand who exactly we are. When we do meet a kindred spirit, it can be earth shattering and life changing, and it's very easy, especially when we're young, to think that the current situation will go on forever, sometimes leading you to take a once-in-a-lifetime experience for granted. As K. and Miu find out, it rarely does. Like the song goes, you don't know what you've got 'til it's gone...
Of course, with Murakami, it's never quite as simple as all that. On top of the nostalgia of lost relationships, 'Sputnik Sweetheart' also deals with a more sinister side of the search for identity. Each of the three central characters experiences a moment where the line between the real world and the imaginary world is blurred, a dangerous time where, if you don't take care, you may end up on the wrong side of the line when the gap closes. Miu's experience on the ferris wheel (the essence of which scene Dan Holloway says he has spent his last two books trying to capture), whether a supernatural moment or a painful psychological projection of self during an unwanted sexual encounter, leaves her empty, broken, unable to function in the real world any more. K., rather more down-to-earth than the others, manages to avoid falling across the line, but is left wondering why he bothered. As for Sumire, well, we'll probably never know.
This book reminds me a little in its themes of 'Norwegian Wood', even if that book is a little more rose-coloured in its portrayal of relationships past (well, vaguely rose-coloured; Murakami is never happy-happy, joy-joy). Most of us can remember times in the past, at school or university, where we met someone with similar interests to us for the first time, and everything just clicked. Many of us are still wondering where that relationship went wrong. Murakami tells us in this book that it's normal for these relationships to fizzle out and for friends to go their separate ways; the satellites cross paths, communicate briefly, then continue their different lonely paths around the earth.